Curtain Size Calculator (Finished Width, Length and Fabric Yardage from Fullness)

Enter the rod width and the height from the carriers (or rings) to the floor or the window sill, in cm. The fullness, fabric width and hems work with their default values. The fabric price can be left blank (then no cost is calculated).

Units

Rod width (cm)

Extra width (%)

Panels Length to

Height from carrier bottom to floor (cm)

Adjustment (cm, ±)

Fullness

Fabric width (cm)

Count fabric widths in

Side hem (each side, cm)

Header (cm)

Bottom hem (cm)

Pattern repeat (cm, 0 if solid)

Fabric price ($/m, optional)

All lengths are in cm. Measure the width between the end carriers or rings that do not move, not from one end of the rod to the other. If you only need the finished length, keep the fabric fields at their defaults.

Result and figure

Enter the rod width, the height, the fullness and so on in the fields on the left and press "Calculate". The result will appear here.

[ CLOSE ]

What you can do on this page
What is this calculation used for?
How to Use
Formulas and figures
Symbols and terms
- Symbols
- Terms
Good to know before you start
How to calculate it in Excel
How to calculate it in Google Sheets
How to calculate it in Python
How to write it in LaTeX and other math languages (copy and paste)
How to have ChatGPT do the calculation
DataChef Features
Related Features
NumberChef Calculators List

What you can do on this page

Enter the rod width and the extra width (ease, 5% by default), and you get the finished width of the curtains (per panel for a pair) on the spot
From the height between the carriers (or rings) and the floor or the window sill, you get a finished length that clears the floor or blocks light below the sill (1/2 in above the floor for floor length, 4 in below the sill for apron length; both can be changed)
From the fullness (1.5×, 2×, flat or your own value) and the fabric width (54 in and others), you get the widths of fabric and the yards needed to sew your own, including side hems, header, hem and rounding up for the pattern repeat
Enter the fabric price per yard to get an estimated cost. The nearest standard ready-made panel sizes (lengths of 63, 84, 95 and 108 in) are shown too as a guide
A front view of the window, rod and curtains shows how the rod width relates to the finished width and length. A plain-language explanation of the formulas and copy-and-paste formulas for Excel, Google Sheets and Python are all on this page

The 1/2 in floor clearance, the 4 in below the sill, the 5% extra width and the hem allowances are all common guidelines. When you order or sew, follow the values given by the store or the fabric maker (or your pattern) first.

What is this calculation used for?

Choosing ready-made curtains after a move

Ready-made curtain panels are sold by width and length, and the most common lengths are 63, 84, 95 and 108 in. For a 72 in rod over a sliding door, the finished width is $72 \times 1.05 = 75.6$ in, or 37.8 in per panel, so a pair of panels at least 38 in wide covers it (the calculator suggests the nearest standard width).
If it is 84 in from the carriers to the floor, the finished length is 83.5 in, but ready-made lengths jump from 63 to 84 in. An 84 in panel would just touch the floor, so you might hang the rod 1/2 in higher, or choose 84 in for a slight "kiss" on the floor. Knowing how far each standard size is from your length helps you decide.

Reading a quote for custom drapes

Price lists for custom drapes are often set by the number of widths (1.5, 2, 2.5 …) and the length, so changing the fullness from 2× to 1.5× can lower the price by reducing the widths.
For example, a panel with a 37.8 in finished width needs a cut width of $37.8 \times 2 + 6 = 81.6$ in at 2× fullness, which is 2 widths of 54 in fabric (in half widths), but only 62.7 in, or 1.5 widths, at 1.5×. These formulas let you check whether the widths on a quote match your own calculation.

Buying fabric to sew your own curtains

When you buy fabric off the bolt, you need to know how many yards to ask for. The widths are sewn side by side, so the length you need is "number of widths × cut length per width".
For 3 widths with a 99.5 in cut length, that is $3 \times 99.5 \div 36 \approx 8.29$ yd. With a patterned fabric and a 27 in repeat, the cut length rounds up to 108 in, and you need $3 \times 108 \div 36 = 9$ yd. Knowing how much the pattern match adds before you buy saves you from running short or buying far too much.

Choosing a length that stops light and drafts below a window

Curtains that end right at the sill let the morning sun in under them, and in winter cold air flows down from the window. A common guideline is to end about 4 in below the sill (apron length); if it is 40 in from the carriers to the sill, the finished length is 44 in.
To cover more of the wall, use +6 in or more; if furniture sits right under the window, use +1 or +2 in. Change the adjustment to find the length that fits your room.

Divider curtains for stores, classrooms and event spaces

Fitting rooms, nap areas in daycares and backstage areas at events are often divided with curtains. To close a 12 ft (144 in) opening with a pair, the finished width is $144 \times 1.05 = 151.2$ in, or 75.6 in per panel. At 2× fullness with 54 in fabric, each panel needs 3 widths, 6 in total. If it is 96 in to the floor (a finished length of 95.5 in) and the cut length after a 27 in pattern match is 135 in, the fabric is $6 \times 135 \div 36 = 22.5$ yd.
More widths mean more fabric and more sewing cost, so this is a guide for choices such as switching to flat panels (1.0–1.3×) to use fewer widths.

Formulas and figures

Finished width (rod width plus extra width)

Figure

Standard notation (the usual math form)

$W$ $=$ $r$ $\times$ $($ $1$ $+$ $e$ $)$

$W_{1}$ $=$ $W$ $\div$ $p$

In words (symbols replaced with words)

③ $W$: finished width (total) $=$ ① $r$: rod width $\times$ $($ $1$ $+$ ② $e$: extra width $)$

⑤ $W_{1}$: finished width per panel $=$ $W$: finished width (total) $\div$ ④ $p$: number of panels

The formula in words

① Take the $r$: rod width

② multiply it by "1 plus the $e$: extra width " (1.05 for 5%)

③ to get the $W$: finished width (total)

④ divide it by the $p$: number of panels (2 for a pair)

⑤ and you get the $W_{1}$: finished width per panel

Quick example

For a 72 in rod, 5% extra width and a pair of panels, the finished width is

$W$: finished width $=$ rod width (72 in) $\times$ $($ $1$ $+$ extra width (0.05) $)$

$72 \times (1 + 0.05) = 72 \times 1.05 = 75.6\,\mathrm{in}$

$75.6 \div 2 = 37.8\,\mathrm{in}$

Key idea

If curtains are made exactly as wide as the rod, gaps open in the middle and at the ends when they are closed, and light leaks through. So they are made a little wider than the rod. This extra width is often 3–5% (5% by default on this page). Measure between the end carriers (or end rings) that do not move, not from one end of the rod to the other. The curtain hooks hang from these, so this length is where the curtains actually hang. For a pair, the total width divided by 2 is the finished width of each panel.

Finished length (measured height plus an adjustment)

Figure

Standard notation (the usual math form)

In words (symbols replaced with words)

$L$ $=$ $h$ $+$ $d$

③ $L$: finished length $=$ ① $h$: measured height $+$ ② $d$: adjustment

The formula in words

① Take the $h$: height measured from the bottom of the carriers to the floor (or the sill)

② add the $d$: adjustment (−0.5 in for floor length, +4 in below the sill as a guide)

③ and you get the $L$: finished length

Quick example

When it is 84 in from the bottom of the carriers to the floor (adjustment −0.5 in), and when it is 40 in from the bottom of the carriers to the sill (adjustment +4 in), the finished lengths are (first line floor length, second line below the sill)

$84 + (-0.5) = 83.5\,\mathrm{in}$

$40 + 4 = 44\,\mathrm{in}$

Key idea

Floor-length curtains that touch the floor get dirty at the hem and drag when you open and close them, so they are usually made about 1/2 in short (they "float" just above the floor). For a window with a sill, curtains that stop right at the sill let light leak under them, so they are made to end about 4 in below the sill (apron length). These are only guidelines. If you like curtains that just kiss the floor, use −0.25 in; for a relaxed look that "breaks" or puddles on the floor, add 1–2 in or more. Measure from the bottom of the carriers (or rings). The hooks hang there, and the fabric falls from that point. Measuring from the top of the rod or from the ceiling makes the curtains too long by the height of the rod. Some hooks hold the curtain so its top sits level with or above the rod to hide it. With that kind of hanging, the store may add the extra height to the length, so follow the store's measuring guide for the hook or heading style you choose.

Cut width per panel (fullness and side hems)

Figure

Standard notation (the usual math form)

$w$ $=$ $W_{1}$ $\times$ $f$ $+$ $2$ $\times$ $s$

In words (symbols replaced with words)

④ $w$: cut width per panel $=$ ① $W_{1}$: finished width per panel $\times$ ② $f$: fullness $+$ $2$ $\times$ ③ $s$: side hem (each side)

The formula in words

① Take the $W_{1}$: finished width per panel

② multiply it by the $f$: fullness (1.5 for 1.5×) to get the width before pleating,

③ add twice the $s$: side hem (each side) (for the left and right edges)

④ and you get the $w$: cut width per panel

Quick example

For a finished width of 37.8 in per panel, 1.5× fullness and a 3 in side hem on each side, the cut width per panel is

$w$: cut width $=$ finished width (37.8 in) $\times$ fullness (1.5) $+$ $2$ $\times$ side hem (3 in)

$37.8 \times 1.5 + 2 \times 3 = 56.7 + 6 = 62.7\,\mathrm{in}$

Key idea

Curtain pleats are made by gathering fabric that is wider than the finished width. How many times the finished width you use is the "fullness". 1.5× and 2× are common, and the higher it is, the deeper and richer the folds, but the more fabric you need. Pinch-pleated drapes often use 2× to 2.5×. Even flat panels with no pleats are often made 1.1–1.3× wide to give a soft wave; 1.0× is completely flat. There are two side hems, left and right, so twice the side hem is added. The value depends on how you fold the hem, so follow your sewing pattern or the workroom's specifications if you have them.

Fabric widths per panel (divide by the fabric width and round up)

Standard notation (the usual math form)

$k$ $=$ $\lceil$ $w$ $\div$ $($ $F$ $\times$ $q$ $)$ $\rceil$ $\times$ $q$

In words (symbols replaced with words)

⑤ $k$: fabric widths per panel $=$ $\lceil$ ① $w$: cut width per panel $\div$ $($ ② $F$: fabric width $\times$ ③ $q$: width step $)$ $\rceil$ $\times$ ④ $q$: width step

The formula in words

① Take the $w$: cut width per panel

② divide it by the $F$: fabric width times

③ $q$: width step (0.5 for half widths, 1 for whole widths) (the width of one step),

④ round up to a whole number of steps (the symbol $\lceil\ \rceil$ means "round up"), and multiply back by the $q$: width step

⑤ to get the $k$: fabric widths per panel

Quick example

For a cut width of 62.7 in, 54 in fabric and half widths (0.5), the fabric widths per panel are (line 1 is the half width, line 2 how many half widths, line 3 the widths)

$k$: widths $=$ $\lceil$ cut width 62.7 in $\div$ $($ fabric width 54 in $\times$ step 0.5 $)$ $\rceil$ $\times$ step 0.5

$54 \times 0.5 = 27\,\mathrm{in}$

$62.7 \div 27 \approx 2.32$

$\lceil 2.32 \rceil \times 0.5 = 3 \times 0.5 = 1.5$

Key idea

Curtain fabric is counted in "widths": one full width of the fabric off the bolt is 1 width. When the cut width of a panel is wider than the fabric, widths are sewn together side by side. Curtain makers often split a width in half lengthwise and add the "half width", which gives panels of 1.5 or 2.5 widths. If you do not want to split the fabric, choose whole widths, and the count is rounded up to whole numbers such as 2 or 3. Some price lists for custom curtains count the side hems as part of the fullness (for example, "a 1.5× panel of 36 in finished width = 1 width of 54 in fabric"). To match that way of counting, set the side hem to 0. The fabric widths to buy $K$ are the widths per panel $k$ times the number of panels $p$, rounded up ($K = \lceil k \times p \rceil$). A pair of 1.5-width panels takes 3 widths in total. A single 1.5-width panel leaves a half width over, so you buy 2 widths. In the example, $1.5 \times 2 = 3$ widths.

Cut length per width (hems and pattern match)

Figure

Standard notation (the usual math form)

$c$ $=$ $L$ $+$ $t$ $+$ $b$

$c'$ $=$ $R$ $\times$ $\lceil$ $c$ $\div$ $R$ $\rceil$

In words (symbols replaced with words)

④ $c$: cut length per width $=$ ① $L$: finished length $+$ ② $t$: header $+$ ③ $b$: bottom hem

⑥ $c'$: cut length after pattern match $=$ ⑤ $R$: pattern repeat $\times$ $\lceil$ $c$: cut length per width $\div$ $R$: pattern repeat $\rceil$

The formula in words

① Take the $L$: finished length

② add the $t$: header

③ and the $b$: bottom hem

④ to get the $c$: cut length per width . For a patterned fabric,

⑤ divide this cut length by the $R$: pattern repeat , round up and multiply back by the repeat

⑥ to get the $c'$: cut length after pattern match (a multiple of the repeat)

Quick example

For a finished length of 83.5 in, an 8 in header and an 8 in bottom hem, the cut length per width is (line 2 is the cut length after the pattern match for a fabric with a 27 in repeat)

$c$: cut length $=$ finished length (83.5 in) $+$ header (8 in) $+$ hem (8 in)

$83.5 + 8 + 8 = 99.5\,\mathrm{in}$

$27 \times \lceil 99.5 \div 27 \rceil = 27 \times \lceil 3.685\cdots \rceil = 27 \times 4 = 108\,\mathrm{in}$

Key idea

The cut length is longer than the finished length. The top is folded over to sew in the buckram or heading tape for the hooks, and the bottom is folded up twice (a double hem). An 8 in header (a double fold around 4 in buckram) and an 8 in bottom hem (4 in folded twice) are guidelines, so change them to match your buckram and the hem you like. With a patterned fabric, widths are matched so the pattern runs on across the seams. To do that, each width has to be cut at a multiple of the pattern repeat, so the cut length is rounded up to a multiple of the repeat. With the 27 in repeat in the example, 99.5 in becomes 108 in, which is 8.5 in more fabric per width. A solid fabric does not need this rounding (when $R = 0$, $c' = c$).

Fabric yardage and estimated cost

Standard notation (the usual math form)

$M$ $=$ $K$ $\times$ $c'$ $\div$ $36$

$T$ $=$ $u$ $\times$ $M$

In words (symbols replaced with words)

③ $M$: fabric needed (yd) $=$ ① $K$: fabric widths to buy $\times$ ② $c'$: cut length after pattern match $\div$ $36$

⑤ $T$: estimated cost $=$ ④ $u$: fabric price ($/yd) $\times$ $M$: fabric needed (yd)

The formula in words

① Take the $K$: fabric widths to buy (widths per panel × panels, rounded up)

② multiply it by the $c'$: cut length after pattern match (in) and divide by 36 to turn inches into yards

③ to get the $M$: fabric needed (yd) . Then multiply by the

④ $u$: fabric price ($/yd)

⑤ to get the $T$: estimated cost

Quick example

For 3 fabric widths, a cut length of 99.5 in per width and fabric at $20 a yard, the fabric needed and the cost are

$M$: fabric needed $=$ widths (3) $\times$ cut length (99.5 in) $\div$ $36$

$3 \times 99.5 \div 36 \approx 8.29\,\mathrm{yd}$

$20 \times 8.2917 \approx 165.83$

Key idea

Fabric is bought by length (by the yard), "number of widths × length of each width". Even though the widths are sewn side by side, they are all cut one after another from the same bolt, so the length you need is the cut length times the number of widths. Stores cut in steps such as 1/8 yd or 1/4 yd, so round the yardage up when you order (8.29 yd is about 8 3/8 yd). The estimated cost is for the fabric only. It does not include sewing labor or supplies such as hooks, buckram and lining. Price lists for custom drapes are often set by "number of widths × length", so the widths and finished length on this page help you read those price lists.

The finished width of curtains is "rod width × (1 + extra width)", and the finished length is "height measured from the carriers ± an adjustment (−1/2 in for floor length, +4 in below the sill as a guide)". For sewing your own, the fabric is the number of widths, found by dividing "finished width × fullness + side hems" by the fabric width and rounding up, times the cut length including the header, hem and pattern match.

Symbols and terms

Symbols

$r$	r	The rod width (the length between the end carriers or rings), from "rail", another word for the rod.
$e$	e	The extra width, from "ease". For 5%, $e = 0.05$ and you multiply by $1 + e = 1.05$.
$p$	p	The number of panels, from "panel". 2 for a pair, 1 for a single panel.
$W$	W	The total finished width (with extra width), from "width". Found with $W = r(1 + e)$.
$W_{1}$	W sub 1	The finished width per panel. Found with $W_{1} = W \div p$.
$h$	h	The height measured from the bottom of the carriers to the floor (floor length) or to the sill, from "height".
$d$	d	The adjustment added to or taken from the measured height. −1/2 in for floor length and +4 in below the sill are common guidelines. Think of "d" for "difference".
$L$	L	The finished length (from the hook position to the hem), from "length". Found with $L = h + d$.
$f$	f	The fullness, from "fullness". 1.5 for 1.5× fullness, 2 for 2×, and 1.0–1.3 for flat panels.
$s$	s	The side hem on one side, from "side". There are two sides, so it is doubled and added.
$w$	w (lowercase)	The cut width per panel (the fabric width before pleating). Found with $w = W_{1} f + 2s$. Lowercase, to tell it apart from the finished width $W$.
$F$	F (capital)	The fabric width (the width off the bolt), from "fabric". Drapery fabric in the US is usually 54 in wide.
$q$	q	The width step. 0.5 when counting in half widths, 1 for whole widths. Think of "q" for "quantum" (a step size).
$k$	k	The fabric widths per panel. Found with $k = \lceil w \div (Fq) \rceil \times q$, written as 1.5 widths, 2 widths and so on.
$K$	K (capital)	The total fabric widths to buy. Found with $K = \lceil k \times p \rceil$ (widths per panel × panels, rounded up).
$t$	t	The header (the fold at the top that holds the buckram), from "top". About 8 in is a common guideline.
$b$	b	The bottom hem (folded up twice and sewn), from "bottom". A 4 in double hem takes about 8 in.
$c$	c	The cut length per width, from "cut". Found with $c = L + t + b$.
$R$	R (capital)	The pattern repeat (the length after which the pattern repeats down the fabric), from "repeat". A solid fabric counts as 0.
$c'$	c prime	The cut length after the pattern match. Found with $c' = R \lceil c \div R \rceil$ (rounded up to a multiple of the repeat). For a solid fabric it equals $c$.
$M$	M	The fabric needed. In yards, $M = K c' \div 36$ (divide by 36 to turn inches into yards); in meters, divide centimeters by 100.
$u$	u	The fabric price per yard, from "unit price".
$T$	T (capital)	The estimated cost (fabric only), from "total". Found with $T = u M$.
$\lceil x \rceil$	ceiling of x	The ceiling function: rounds up to the next whole number. (Examples: $\lceil 2.32 \rceil = 3$, $\lceil 3 \rceil = 3$)

Terms

curtain rod	The rod that curtains hang from. A traverse rod has carriers that slide inside it, and a decorative rod has rings that slide along a wooden or metal pole. On both, measure the width between the end carriers (or end rings), not the whole rod, and measure the height from the bottom of the carriers or rings.
carrier	A small slider that runs inside a curtain rod and holds a curtain hook. The ones at each end that do not move are the end carriers, and both the width and the height are measured from them.
floor length	Curtains that reach the floor, used for tall windows and sliding glass doors. They are usually made about 1/2 in short so they do not touch the floor.
apron length	Curtains that end about 4 in below the window sill. Stopping below the sill keeps light from leaking under the curtains. (Sill length ends right at the sill.)
extra width	The share by which curtains are made wider than the rod, so no gap opens in the middle or at the ends when they are closed. 3–5% is common.
finished width	The width of the finished curtains. For a pair, each panel is half of the total.
finished length	The length of the finished curtains, from the hook position (the bottom of the carriers) to the hem.
pair	Two panels that open from the center to both sides. Most windows use a pair.
single panel	One curtain that draws to one side, used for small windows and as a room divider.
fullness	How many times the finished width of fabric is gathered into pleats. 1.5× and 2× are common, and higher fullness gives deeper, richer folds.
2-finger pleat	A pinch pleat with two folds. It suits a lighter fullness, such as 1.5×.
3-finger pleat	A pinch pleat with three folds, the classic pinch pleat. It suits 2× fullness or more and gives a rich look.
flat panel	A curtain with no pleats, such as a rod pocket or grommet panel. It is often made 1.1–1.3× wide for a soft wave; 1.0× is completely flat.
width	In curtain making, one full width of fabric off the bolt counts as 1 width. Widths are sewn side by side to make a panel, described as "2 widths", "1.5 widths" and so on.
fabric widths	How many widths of fabric are sewn side by side in one panel. Price lists for custom drapes are often set by the number of widths and the length.
half width	A width of fabric split in half lengthwise (0.5 width). Panels of 1.5 or 2.5 widths are made by adding a half width to one or both sides.
fabric width	The width of the fabric on the bolt. Drapery fabric in the US is usually 54 in wide, and some wide fabrics are about 118 in.
side hem	The extra fabric at each side edge that is folded and sewn. A 1.5 in double-fold side hem takes 3 in per side.
header	The extra length folded over at the top to hold the buckram or heading tape (about 8 in around 4 in buckram). The bottom hem is folded up twice (about 8 in for a 4 in double hem).
buckram	A stiff band sewn into the top of a curtain. It holds the hooks and keeps the pleats in shape. 4 in buckram is common for pinch pleats.
pattern repeat	The length after which the pattern repeats down the fabric. Each cut length is rounded up to a multiple of it so the pattern lines up across the widths.
pattern match	Lining up the pattern so it runs on across the seams between widths. It takes extra fabric for each width.
ready-made curtains	Curtains made and sold in set sizes. In the US, common lengths are 63, 84, 95 and 108 in, and the choice of widths differs by store and style.
custom drapes	Curtains made to the exact size of your window. Prices are often set by a table of widths × length.
rounding up	Changing a value with a decimal part to the next whole number (or the next step). The number of widths and repeats must be rounded up so you do not run short.

Good to know before you start

Here is what helps you use the calculation on this page with real understanding, not just by pressing the button.

Percentages (Grades 6–7)	Knowing that "5% more" can be calculated as "× 1.05" Knowing that "1.5 times" or "2 times" a length is found by multiplication
Multiplying and dividing decimals (Grades 5–6)	Understanding what decimal calculations such as $37.8 \times 1.5$ and $62.7 \div 27$ mean (a calculator is fine for the arithmetic)
Adding positive and negative numbers (Grade 7)	Knowing that adding a negative adjustment, as in "84 + (−0.5)", is the same as subtracting 0.5
Converting units of length (Grades 4–5)	Knowing that 1 yd = 36 in, so 298.5 in is about 8.29 yd
Rounding (Grades 3–4)	Knowing the difference between rounding up, rounding down and rounding to the nearest Being able to explain in your own words why you round up the number of widths and repeats
Multiples (Grades 4–5)	Knowing that "the smallest multiple of 27 that is at least 99.5" is 108 (the idea behind rounding up to the pattern repeat)

How to calculate it in Excel

Copy the whole table below and paste it into cell A1 in Excel. It works as is.

Table to find the finished width

Rod width (in)	72
Extra width (%)	5
Panels (pair = 2, single = 1)	2
Finished width (total, in)	=B1*(1+B2/100)
Finished width per panel (in)	=B4/B3

Table to find the finished length

Height measured from the carriers (in)	84
Adjustment (in; floor length -0.5, below the sill 4)	-0.5
Finished length (in)	=B1+B2

Table to find the cut width per panel

Finished width per panel (in)	37.8
Fullness	1.5
Side hem (each side, in)	3
Cut width per panel (in)	=B1B2+2B3

Table to find the fabric widths per panel

Cut width per panel (in)	62.7
Fabric width (in)	54
Width step (half = 0.5, whole = 1)	0.5
Panels	2
Fabric widths per panel	=ROUNDUP(B1/(B2B3),0)B3
Fabric widths to buy (total)	=ROUNDUP(B5*B4,0)

Table to find the cut length per width

Finished length (in)	83.5
Header (in)	8
Bottom hem (in)	8
Pattern repeat (in, 0 if solid)	0
Cut length per width (in)	=B1+B2+B3
Cut length after pattern match (in)	=IF(B4>0,B4*ROUNDUP(B5/B4,0),B5)

Table to find the fabric yardage and the estimated cost

Fabric widths to buy (total)	3
Cut length after pattern match (in)	99.5
Fabric price ($/yd)	20
Fabric needed (yd)	=B1*B2/36
Estimated cost ($)	=B3*B4

After pasting, the upper rows in column B are your inputs and the last rows are calculated automatically.
"ROUNDUP(value, 0)" rounds up to a whole number (the ⌈ ⌉ in the formulas). The fourth table divides the cut width by "fabric width × step", rounds up and multiplies back by the step, so the widths come out in half widths (0.5) directly.
"IF(B4>0, …)" in the fifth table skips the rounding when the pattern repeat is 0 (a solid fabric).
With the example numbers, B5 in the first table shows 37.8, B3 in the second 83.5, B4 in the third 62.7, B5 and B6 in the fourth 1.5 and 3, B6 in the fifth 99.5 (108 if you enter a repeat of 27), and B4 and B5 in the sixth about 8.29 and 165.83. Just replace the numbers in column B with your own.

How to calculate it in Google Sheets

Copy the whole table below and paste it into cell A1 in Google Sheets. It works as is.

Table to find the finished width

Rod width (in)	72
Extra width (%)	5
Panels (pair = 2, single = 1)	2
Finished width (total, in)	=B1*(1+B2/100)
Finished width per panel (in)	=B4/B3

Table to find the finished length

Height measured from the carriers (in)	84
Adjustment (in; floor length -0.5, below the sill 4)	-0.5
Finished length (in)	=B1+B2

Table to find the cut width per panel

Finished width per panel (in)	37.8
Fullness	1.5
Side hem (each side, in)	3
Cut width per panel (in)	=B1B2+2B3

Table to find the fabric widths per panel

Cut width per panel (in)	62.7
Fabric width (in)	54
Width step (half = 0.5, whole = 1)	0.5
Panels	2
Fabric widths per panel	=ROUNDUP(B1/(B2B3),0)B3
Fabric widths to buy (total)	=ROUNDUP(B5*B4,0)

Table to find the cut length per width

Finished length (in)	83.5
Header (in)	8
Bottom hem (in)	8
Pattern repeat (in, 0 if solid)	0
Cut length per width (in)	=B1+B2+B3
Cut length after pattern match (in)	=IF(B4>0,B4*ROUNDUP(B5/B4,0),B5)

Table to find the fabric yardage and the estimated cost

Fabric widths to buy (total)	3
Cut length after pattern match (in)	99.5
Fabric price ($/yd)	20
Fabric needed (yd)	=B1*B2/36
Estimated cost ($)	=B3*B4

The same formulas as in Excel (including the ROUNDUP and IF functions) work as is. Copy the whole table, paste it into cell A1, and replace the numbers in column B with your own.

How to calculate it in Python

import math

rod_width_in = 72        # rod width (between the end carriers, in)
extra_percent = 5        # extra width (%)
panels = 2               # panels (pair = 2, single = 1)
height_in = 84           # height from the bottom of the carriers to the floor (or the sill), in
adjust_in = -0.5         # adjustment (-0.5 for floor length, 4 below the sill, as a guide)
fullness = 1.5           # fullness (1.5x = 1.5, 2x = 2, flat = 1.0 to 1.3)
fabric_width_in = 54     # fabric width (in)
width_step = 0.5         # width step (half widths = 0.5, whole widths = 1)
side_hem_in = 3          # side hem (each side, in)
header_in = 8            # header (in)
bottom_hem_in = 8        # bottom hem (in)
repeat_in = 0            # pattern repeat (in, 0 if solid)
price_per_yd = 20        # fabric price ($ per yard)

finish_width = rod_width_in * (1 + extra_percent / 100)          # finished width (total)
panel_width = finish_width / panels                              # finished width per panel
finish_length = height_in + adjust_in                            # finished length

cut_width = panel_width * fullness + 2 * side_hem_in             # cut width per panel
widths_per_panel = math.ceil(cut_width / (fabric_width_in * width_step)) * width_step   # fabric widths per panel (rounded up)
widths_total = math.ceil(widths_per_panel * panels)              # fabric widths to buy (total, rounded up)

cut_length = finish_length + header_in + bottom_hem_in           # cut length per width
if repeat_in > 0:
    cut_length = repeat_in * math.ceil(cut_length / repeat_in)   # pattern match (round up to a multiple of the repeat)

fabric_yd = widths_total * cut_length / 36                       # fabric needed (yd)
cost = price_per_yd * fabric_yd                                  # estimated cost ($)

print(f"Finished width: {finish_width:.1f} in ({panel_width:.1f} in per panel)")
print(f"Finished length: {finish_length} in")
print(f"Cut width per panel: {cut_width:.1f} in -> {widths_per_panel} widths per panel, {widths_total} in total")
print(f"Cut length per width: {cut_length} in")
print(f"Fabric needed: {fabric_yd:.2f} yd")
print(f"Estimated cost: ${cost:,.2f}")

Runs with the standard library only. math.ceil() rounds up (the ⌈ ⌉ in the formulas). Replace the sizes, fullness and price at the top with your own numbers and run it. For curtains below the sill, set adjust_in to 4; if the finished length is already decided, put that value in finish_length directly.

How to write it in LaTeX and other math languages (copy and paste)

Finished width (rod width plus extra width)

W = r × (1 + e),  W₁ = W ÷ p

W = r(1 + e),\quad W_{1} = \frac{W}{p}

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>W</mi><mo>=</mo><mi>r</mi><mo>&#x2062;</mo>
    <mrow><mo>(</mo><mn>1</mn><mo>+</mo><mi>e</mi><mo>)</mo></mrow>
    <mo>,</mo>
    <msub><mi>W</mi><mn>1</mn></msub><mo>=</mo>
    <mfrac><mi>W</mi><mi>p</mi></mfrac>
  </mrow>
</math>

W = r (1 + e),  W_1 = W / p

W = r*(1 + e); W1 = W/p

W := r*(1 + e);  W1 := W/p;

W = r*(1 + e); W1 = W/p;

W = r(1 + e), W_1 = W/p

Finished length (measured height plus an adjustment)

L = h + d

L = h + d

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>L</mi><mo>=</mo><mi>h</mi><mo>+</mo><mi>d</mi>
  </mrow>
</math>

L = h + d

L = h + d

L := h + d;

L = h + d;

L = h + d

Cut width per panel (fullness and side hems)

w = W₁ × f + 2s

w = W_{1} f + 2s

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>w</mi><mo>=</mo>
    <msub><mi>W</mi><mn>1</mn></msub><mo>&#x2062;</mo><mi>f</mi>
    <mo>+</mo><mn>2</mn><mo>&#x2062;</mo><mi>s</mi>
  </mrow>
</math>

w = W_1 f + 2 s

w = W1*f + 2*s

w := W1*f + 2*s;

w = W1*f + 2*s;

w = W_1 f + 2s

Fabric widths per panel (divide by the fabric width and round up)

k = ⌈w ÷ (F × q)⌉ × q

k = \left\lceil \frac{w}{F q} \right\rceil q

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>k</mi><mo>=</mo>
    <mo>&#x2308;</mo>
    <mfrac><mi>w</mi><mrow><mi>F</mi><mo>&#x2062;</mo><mi>q</mi></mrow></mfrac>
    <mo>&#x2309;</mo>
    <mo>&#x2062;</mo><mi>q</mi>
  </mrow>
</math>

k = |~ w / (F q) ~| q

k = Ceiling[w/(F*q)]*q

k := ceil(w/(F*q))*q;

k = ceil(w/(F*q))*q;

k = ⌈w/(F q)⌉ q

Cut length per width (hems and pattern match)

c = L + t + b,  c′ = R × ⌈c ÷ R⌉

c = L + t + b,\quad c' = R \left\lceil \frac{c}{R} \right\rceil

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>c</mi><mo>=</mo><mi>L</mi><mo>+</mo><mi>t</mi><mo>+</mo><mi>b</mi>
    <mo>,</mo>
    <msup><mi>c</mi><mo>&#x2032;</mo></msup><mo>=</mo>
    <mi>R</mi><mo>&#x2062;</mo>
    <mo>&#x2308;</mo><mfrac><mi>c</mi><mi>R</mi></mfrac><mo>&#x2309;</mo>
  </mrow>
</math>

c = L + t + b,  c' = R |~ c / R ~|

c = L + t + b; cAdj = R*Ceiling[c/R]

c := L + t + b;  c2 := R*ceil(c/R);

c = L + t + b; c2 = R*ceil(c/R);

c = L + t + b, c′ = R⌈c/R⌉

Fabric yardage and estimated cost

M = K × c′ ÷ 36,  T = u × M

M = \frac{K c'}{36},\quad T = u M

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>M</mi><mo>=</mo>
    <mfrac><mrow><mi>K</mi><mo>&#x2062;</mo><msup><mi>c</mi><mo>&#x2032;</mo></msup></mrow><mn>36</mn></mfrac>
    <mo>,</mo>
    <mi>T</mi><mo>=</mo><mi>u</mi><mo>&#x2062;</mo><mi>M</mi>
  </mrow>
</math>

M = (K c') / 36,  T = u M

M = kTotal*cAdj/36; T = u*M

M := K*c2/36;  T := u*M;

M = K*c2/36; T = u*M;

M = K c′/36, T = u M

How to have ChatGPT do the calculation

You are an assistant for curtain measuring and sewing quantities. Do the following calculation by actually running Python code, and base your answer only on the numbers from the execution result (do not answer by mental math or guessing).

The rod width (between the end carriers) is 72 in, the extra width is 5%, and it is a pair of floor-length curtains. The height from the bottom of the carriers to the floor is 84 in (make them 1/2 in short so they do not touch the floor).
I use 1.5x fullness, 54 in wide fabric (joined in half widths), side hems of 3 in on each side, an 8 in header, an 8 in bottom hem and a solid fabric.
Find each of the following:
1. The total finished width and the finished width per panel
2. The finished length
3. The cut width per panel (finished width × fullness + side hem × 2)
4. The fabric widths per panel (cut width ÷ half width, rounded up, in steps of 0.5) and the total widths to buy
5. The cut length per width (finished length + header + bottom hem) and the yards of fabric needed

Show the formulas you used and the numbers from the execution result.

How to Use

1

Enter your numbers

Type the numbers you want to calculate with into the input fields
2

Calculate

Press the "Calculate" button
3

Check the result

The result appears on the spot. The same page also explains the idea behind the calculation and the formula

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\(r\)	r	The rod width (the length between the end carriers or rings), from "rail", another word for the rod.
\(e\)	e	The extra width, from "ease". For 5%, \(e = 0.05\) and you multiply by \(1 + e = 1.05\).
\(p\)	p	The number of panels, from "panel". 2 for a pair, 1 for a single panel.
\(W\)	W	The total finished width (with extra width), from "width". Found with \(W = r(1 + e)\).
\(W_{1}\)	W sub 1	The finished width per panel. Found with \(W_{1} = W \div p\).
\(h\)	h	The height measured from the bottom of the carriers to the floor (floor length) or to the sill, from "height".
\(d\)	d	The adjustment added to or taken from the measured height. −1/2 in for floor length and +4 in below the sill are common guidelines. Think of "d" for "difference".
\(L\)	L	The finished length (from the hook position to the hem), from "length". Found with \(L = h + d\).
\(f\)	f	The fullness, from "fullness". 1.5 for 1.5× fullness, 2 for 2×, and 1.0–1.3 for flat panels.
\(s\)	s	The side hem on one side, from "side". There are two sides, so it is doubled and added.
\(w\)	w (lowercase)	The cut width per panel (the fabric width before pleating). Found with \(w = W_{1} f + 2s\). Lowercase, to tell it apart from the finished width \(W\).
\(F\)	F (capital)	The fabric width (the width off the bolt), from "fabric". Drapery fabric in the US is usually 54 in wide.
\(q\)	q	The width step. 0.5 when counting in half widths, 1 for whole widths. Think of "q" for "quantum" (a step size).
\(k\)	k	The fabric widths per panel. Found with \(k = \lceil w \div (Fq) \rceil \times q\), written as 1.5 widths, 2 widths and so on.
\(K\)	K (capital)	The total fabric widths to buy. Found with \(K = \lceil k \times p \rceil\) (widths per panel × panels, rounded up).
\(t\)	t	The header (the fold at the top that holds the buckram), from "top". About 8 in is a common guideline.
\(b\)	b	The bottom hem (folded up twice and sewn), from "bottom". A 4 in double hem takes about 8 in.
\(c\)	c	The cut length per width, from "cut". Found with \(c = L + t + b\).
\(R\)	R (capital)	The pattern repeat (the length after which the pattern repeats down the fabric), from "repeat". A solid fabric counts as 0.
\(c'\)	c prime	The cut length after the pattern match. Found with \(c' = R \lceil c \div R \rceil\) (rounded up to a multiple of the repeat). For a solid fabric it equals \(c\).
\(M\)	M	The fabric needed. In yards, \(M = K c' \div 36\) (divide by 36 to turn inches into yards); in meters, divide centimeters by 100.
\(u\)	u	The fabric price per yard, from "unit price".
\(T\)	T (capital)	The estimated cost (fabric only), from "total". Found with \(T = u M\).
\(\lceil x \rceil\)	ceiling of x	The ceiling function: rounds up to the next whole number. (Examples: \(\lceil 2.32 \rceil = 3\), \(\lceil 3 \rceil = 3\))

Curtain Size Calculator (Finished Width, Length and Fabric Yardage from Fullness)

Table of Contents

What you can do on this page

What is this calculation used for?

Formulas and figures

Symbols and terms

Symbols

Terms

Good to know before you start

How to calculate it in Excel

How to calculate it in Google Sheets

How to calculate it in Python

How to write it in LaTeX and other math languages (copy and paste)

How to have ChatGPT do the calculation

How to Use

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