Blind and Shade Size Calculator (Inside and Outside Mount)

Choose the mount type (inside or outside) and the product, then enter the window width and height in cm. The deductions and overlaps are already filled in for the product, so you can calculate as is. The price can be left blank (then no cost is calculated).

Units

Mount type Product Window 1

Inside width (cm)

Inside height (cm)

Window 2 (optional)

Inside width (cm)

Inside height (cm)

Window 3 (optional)

Inside width (cm)

Inside height (cm)

Width deduction (total, cm)

Height deduction (cm)

Rounding the order size Price type (optional)

Price per m² ($, optional)

All lengths are in cm. For an inside mount, measure the inside width and height of the frame; for an outside mount, the outside width and height. Measure the width at the top, middle and bottom and the height at the left, middle and right. Use the smallest value for an inside mount and the largest for an outside mount to be safe.

Result and figure

Enter the mount type and the window size 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

For an inside mount (inside the window frame), subtract the deduction (1/4 in by default, which you can change) from the inside width and height of the frame and see the order size right away
For an outside mount (on the wall around the window), add an overlap on each side (about 1.5 in) and room at the top and bottom (about 1.5 in each) to the outside size of the frame
Choose the product (horizontal blinds, roller shades, pleated or cellular shades, vertical blinds) and the default deductions and overlaps switch to common values for that product
The order size is rounded to 1/8 in (or 1/4 in): down for an inside mount and up for an outside mount. Enter up to 3 windows to get the total area and a cost estimate from a price per ft² or a price per window
A front view of the window and the product shows where to measure and how much to subtract or add. A plain explanation of the formulas and copy-and-paste formulas for Excel, Google Sheets and Python are on this page too

The default deductions and overlaps are common guidelines. The real values and each product's size limits (minimum and maximum width and height) differ by maker and product, so always check the maker's specs and measuring guide before you order. This page does not cover the cord or wand position. For fabric curtains, use the curtain size page. Switch "Units" above the calculator to Metric to work in centimeters.

What is this calculation used for?

Putting blinds on a rental window without drilling the wall

In a rental it is hard to drill into the walls, so an inside mount is a common choice (the screw holes go into the window frame instead, so check that with your landlord too). For a window with an inside size of 68 in × 48 in, with 1/4 in deductions for the width and height, the order size is $67\tfrac{3}{4} \times 47\tfrac{3}{4}$ in.
An order at the exact inside size may not fit the frame, so the basic rule is to order the size minus the deduction (or give the exact size to a store that deducts for you). Frames are often out of square, so measure the width and height three times each and use the smallest value.

Covering the whole bedroom window with an outside mount to block light

In a bedroom where the morning sun wakes you up, or a room with strong afternoon sun, an outside mount that covers the whole frame reduces light leaking around the edges. For a window with an outside size of 72 in × 52 in, with overlaps of 1.5 in on each side, at the top and at the bottom, the order size is $75 \times 55$ in.
Roller shade fabric is a little narrower than the headrail (often about 1 to 1.5 in in total, depending on the product). If blocking light matters most, you can try wider side overlaps, such as 3 in per side for $78 \times 55$ in, right on the spot with this formula.

A roller shade for a small bathroom or kitchen window

For small bathroom and kitchen windows, which get splashed with water and grease, wipeable roller shades or blinds work better than curtains. For a small window with an inside size of 24 in × 20 in and an inside mount, the order size is $23\tfrac{3}{4} \times 19\tfrac{3}{4}$ in.
The smaller the window, the more likely it is to fall below a product's minimum size (often around 1 to 2 ft for width and height), so check in the maker's specs that the order size is at least the minimum.

Estimating several office or store windows at once

When you remodel an office or store, you often order the same blinds for many windows at once. For two windows with an inside size of 68 in × 48 in and one of 36 in × 44 in, the inside-mount area (1/4 in deductions) is $22.4657 + 22.4657 + 10.8615 \approx 55.79$ ft².
At $6.50 per ft², that is about $362.65, which you can compare with the total of the window prices on a quote. Installation and shipping are separate, so also check the breakdown on the quote.

Vertical blinds for a patio door

Vertical blinds that open to the side are a common choice for a sliding patio door in the living room. For an outside mount with an outside size of 76 in wide and 82 in high, and 84 in from the top of the frame to the floor, use a 4 in overlap per side, 1.5 in of room at the top and a 1.5 in overlap at the bottom so the vanes clear the floor (84 + 1.5 − 0.5 − 82 − 1.5). The order size is $84 \times 85$ in.
A very wide opening can exceed one product's maximum size, and then you order two. Either way, check that the bottom of the vanes will not touch the floor.

Formulas and figures

Inside mount order size (inside size minus the deduction)

Figure

Standard notation (the usual math form)

$W$ $=$ $w$ $-$ $a$

$H$ $=$ $h$ $-$ $b$

In words (symbols replaced with words)

③ $W$: order width $=$ ① $w$: inside width $-$ ② $a$: width deduction (total)

⑥ $H$: order height $=$ ④ $h$: inside height $-$ ⑤ $b$: height deduction

The formula in words

① From the $w$: inside width, measured inside the frame

② subtract the $a$: width deduction (about 1/4 in in total)

③ to get the $W$: order width

④ In the same way, from the $h$: inside height

⑤ subtract the $b$: height deduction (about 1/4 in at the bottom)

⑥ to get the $H$: order height

Quick example

For a window frame with an inside size of 68 in wide and 48 in high, with a 1/4 in width deduction (total) and a 1/4 in height deduction, the order size is (first line width, second line height)

order width $W$ $=$ inside width (68 in) $-$ deduction (1/4 in)

$68 - 0.25 = 67.75\,\mathrm{in} = 67\tfrac{3}{4}\,\mathrm{in}$

$48 - 0.25 = 47.75\,\mathrm{in} = 47\tfrac{3}{4}\,\mathrm{in}$

Key idea

An inside mount hangs the product from brackets on the top of the opening, inside the window frame. The product sits completely inside the frame, so if you make it the exact inside size, it may not fit or it may rub the frame every time you raise and lower it. So you order it a little smaller than the inside size: that is the deduction. About 1/4 in in total for the width is common, and about 1/4 in for the height so the bottom rail does not hit the sill when lowered. Vertical blinds swing in the wind, so their height deduction is often larger, about 1/2 in. Window frames are often slightly out of square, so measure the width at the top, middle and bottom and the height at the left, middle and right, and use the smallest value as the inside size. Many US stores ask for the exact inside size and make the deduction at the factory. If yours does, set the deduction to 0 in the calculator. An inside mount needs no holes in the wall (the screws go into the top of the frame) and looks neat, but there are gaps between the frame and the product. For room darkening, an outside mount works better.

Outside mount order size (outside size plus the overlaps)

Figure

Standard notation (the usual math form)

$W$ $=$ $w$ $+$ $2$ $\times$ $c$

$H$ $=$ $h$ $+$ $t$ $+$ $d$

In words (symbols replaced with words)

③ $W$: order width $=$ ① $w$: outside width $+$ $2$ $\times$ ② $c$: side overlap (each side)

⑦ $H$: order height $=$ ④ $h$: outside height $+$ ⑤ $t$: room at the top $+$ ⑥ $d$: overlap at the bottom

The formula in words

① To the $w$: outside width, measured outside the frame

② add twice the $c$: side overlap (about 1.5 in per side) (one for each side)

③ to get the $W$: order width

④ In the same way, to the $h$: outside height

⑤ add the $t$: room at the top (for the brackets and headrail, about 1.5 in)

⑥ and the $d$: overlap at the bottom (about 1.5 in)

⑦ to get the $H$: order height

Quick example

For a window with an outside size of 72 in wide and 52 in high, with a 1.5 in overlap on each side, 1.5 in of room at the top and a 1.5 in overlap at the bottom, the order size is (first line width, second line height)

order width $W$ $=$ outside width (72 in) $+$ $2$ $\times$ side overlap (1.5 in)

$72 + 2 \times 1.5 = 75\,\mathrm{in}$

$52 + 1.5 + 1.5 = 55\,\mathrm{in}$

Key idea

An outside mount puts the brackets on the wall or on the face of the trim around the window, so the product covers the whole window, frame and all. The product is larger than the frame, so less light leaks around it, which suits bedrooms you want dark or rooms with strong afternoon sun. How much larger is the overlap: about 1.5 in per side (3 in in total), about 1.5 in at the top for the brackets and headrail, and about 1.5 in at the bottom are common. For vertical blinds or better light blocking, some people widen the sides to about 4 in each. The room at the top depends on where there is solid wood for the screws. On drywall, brackets can only go where there is a stud, header or other framing behind the wall, so set the top room to reach it. Also check before ordering that wall bumps, an air conditioner or a curtain rod will not get in the way. For a patio door or other glass that reaches the floor, set the bottom overlap so the order height is about "distance from the product top (frame top + top room) to the floor − 1/2 in", and the product will not drag on the floor. Roller shade fabric is usually a little narrower than the headrail (often about 1 to 1.5 in in total, depending on the product), so if light leaks bother you, add that much to the side overlaps.

Area and estimated cost

Standard notation (the usual math form)

$A$ $=$ $W$ $\times$ $H$ $\div$ $144$

$T$ $=$ $u$ $\times$ $A$

In words (symbols replaced with words)

③ $A$: area (ft²) $=$ ① $W$: order width (in) $\times$ ② $H$: order height (in) $\div$ $144$

⑤ $T$: estimated cost $=$ ④ $u$: price per ft² ($) $\times$ $A$: area (ft²)

The formula in words

① Multiply the $W$: order width (in)

② by the $H$: order height (in) and divide by 144 to change it to square feet,

③ to get the $A$: area (ft²)

④ Then multiply by the $u$: price per ft² ($)

⑤ to get the $T$: estimated cost

Quick example

For an order size of 67.75 in wide and 47.75 in high at $6.50 per ft², the area and estimated cost are

area $A$ $=$ order width (67.75 in) $\times$ order height (47.75 in) $\div$ $144$

$67.75 \times 47.75 \div 144 = 3235.0625 \div 144 \approx 22.47\,\mathrm{ft^2}$

$6.50 \times 22.4657 \approx 146.03$

Key idea

Multiplying the width and height in inches gives square inches (in²). 1 ft = 12 in, so 1 ft² = 12 in × 12 in = 144 in², and dividing by 144 changes it to ft². For several windows, find each area with this formula and add them up for the total area. (In metric, cm × cm ÷ 10,000 gives m².) Blinds and shades are usually priced from a "width × height" price grid, so a cost from a price per ft² is only an estimate. If you know each window's price from a quote or price list, choose "Price per window" and enter them; their total is the estimated cost ($T = p_1 + p_2 + p_3$). Installation, shipping and options such as cordless lift or motorization are not included. Before ordering, always check the maker's specs to see that the order size is within the product's size limits (minimum and maximum width and height). A very large window may need two products instead of one.

For an inside mount, the order size is the inside size of the frame minus the deduction (about 1/4 in for the width and height). For an outside mount, it is the outside size plus the overlaps (about 1.5 in per side, top and bottom). Round the order size to 1/8 in, down for an inside mount and up for an outside mount. Width × height ÷ 144 gives the area in ft², and times the price per ft² gives an estimated cost.

Symbols and terms

Symbols

$w$	lowercase double-u	The window width. Measure the inside width for an inside mount and the outside width for an outside mount. It comes from "width", and it is lowercase to tell it apart from the order width $W$.
$h$	lowercase aitch	The window height - the inside height for an inside mount and the outside height for an outside mount. It comes from "height".
$a$	ay	The width deduction for an inside mount (both sides together). About 1/4 in is common. Think of it as "allowance".
$b$	bee	The height deduction for an inside mount (at the bottom). About 1/4 in is common, and about 1/2 in for vertical blinds. Think of it as "bottom".
$W$	capital double-u	The order width (the product width). It is $W = w - a$ for an inside mount and $W = w + 2c$ for an outside mount.
$H$	capital aitch	The order height (the product height). It is $H = h - b$ for an inside mount and $H = h + t + d$ for an outside mount.
$c$	cee	The side overlap for an outside mount (each side). There are two sides, so add it twice. About 1.5 in per side is common. Think of it as "cover".
$t$	tee	The room at the top for an outside mount, for the brackets and headrail above the frame. About 1.5 in is common. It comes from "top".
$d$	dee	The overlap at the bottom for an outside mount, how far it hangs below the frame. About 1.5 in is common. Think of it as "down".
$A$	capital ay	The product area (ft²). It is found with $A = W \times H \div 144$. It comes from "area".
$u$	you	The price per ft² ($ per square foot of product). It comes from "unit price".
$p$	pee	The price per window (for that window's product). With three windows, they are numbered $p_1, p_2, p_3$. It comes from "price".
$T$	capital tee	The total estimated cost. It is $T = u \times A$ with a price per ft², or $T = p_1 + p_2 + p_3$ with prices per window. It comes from "total".
$\mathrm{ft^2}$	square feet	A unit of area: a square 1 ft on each side, also written sq ft. $1\,\mathrm{ft^2} = 144\,\mathrm{in^2}$ (and $1\,\mathrm{m^2} \approx 10.76\,\mathrm{ft^2}$).

Terms

Inside mount	Mounting the product with brackets on the top of the opening inside the window frame. It sits inside the frame and looks neat, and needs no holes in the wall (the screws go into the frame). Light can leak through the gaps, and the order size is smaller than the inside size by the deduction.
Outside mount	Mounting the product with brackets on the wall around the window or on the face of the trim. It covers the whole window, so less light leaks, which suits rooms you want dark. The order size is larger than the outside size by the overlaps.
Inside width and height	The size measured inside the window frame, from the inner face on the left to the right and from the top to the bottom. For an inside mount, subtract the deduction from it.
Outside width and height	The size measured outside the window trim, from the outer edge on the left to the right and from the top to the bottom. For an outside mount, add the overlaps to it.
Deduction	For an inside mount, the amount the product is made smaller than the inside size so it fits without rubbing. About 1/4 in for the width and 1/4 in for the height are common, but it differs by maker and product. Many US stores make this deduction at the factory.
Overlap	For an outside mount, how far the product extends past the frame to stop light leaking. About 1.5 in per side, 1.5 in at the top for mounting and 1.5 in at the bottom are common.
Horizontal blinds	A product with many horizontal slats that tilt to control the light. Aluminum mini blinds are common, and wood and faux wood blinds too. For an inside mount, the height deduction keeps the bottom rail from hitting the sill.
Roller shade	A single piece of fabric that rolls up onto a tube at the top. The fabric is a little narrower than the headrail (often about 1 to 1.5 in in total, depending on the product), so for fewer light leaks, use an outside mount with extra side overlap.
Pleated shade	A shade of fabric folded like an accordion that stacks up when raised. Some combine two fabrics (top-down/bottom-up). Measure it the same way as horizontal blinds.
Cellular shade (honeycomb)	A kind of pleated shade whose fabric forms honeycomb-shaped cells. The air in the cells insulates, reducing heat loss and gain through the window. Measure it the same way as a pleated shade.
Vertical blinds	A product with long vertical vanes side by side that open to the left or right. They swing in a breeze and can hit the floor or sill, so for an inside mount, use a larger height deduction, about 1/2 in.
Headrail	The top part of a blind or shade that holds the lift and tilt mechanism; the brackets hold it. For an outside mount, add room at the top for it above the frame.
Bottom rail	The bar at the very bottom of a horizontal blind. It also weighs the slats down so they hang straight. For an inside mount, the height deduction keeps it from hitting the sill.
Vanes (louvers)	The long vertical slats of vertical blinds. They turn to control the light and stack to one side to open.
Slats	The individual horizontal pieces of a blind. Common widths include 1 in (mini blinds) and 2 in (wood and faux wood). They tilt to control the light.
Window trim (casing)	The wood or vinyl trim around a window. An inside mount goes on the top of the opening inside it; an outside mount goes on the wall outside it or on its face.
Patio door	A large glass door that reaches the floor, often a sliding glass door to a deck or yard. For an outside mount, set the bottom overlap so the product is about 1/2 in shorter than the distance from its top to the floor.
Stud (solid backing)	The wood framing behind the wall (studs and headers) that holds screws firmly. Screws do not hold in drywall alone, so put outside-mount brackets where there is framing, or use suitable anchors.
Size limits	The smallest and largest width and height a product can be made in. They differ by maker, product and lift type, and sizes outside the range cannot be ordered. Always check the maker's specs before ordering.
Price per square foot	The price per ft² of product. Blinds and shades are usually priced from a "width × height" price grid, so a cost from a price per square foot is an estimate.
Rounding down	Dropping the part below the chosen step to get the smaller value. Inside-mount order sizes are rounded down so they fit the frame (for example 67.80 in → 67 3/4 in).
Rounding up	Moving to the larger value if there is any part below the chosen step. Outside-mount order sizes are rounded up so they cover the window (for example 75.05 in → 75 1/8 in).

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.

Decimals and the order of operations (Grades 5–6)	Doing addition, subtraction and multiplication with decimals in the right order, such as $68.3 - 0.25$ and $72 + 2 \times 1.5$ (multiplication comes first)
Fractions of an inch and units of length (Grades 4–5)	Reading a tape measure to 1/8 in and writing fractions as decimals: 1/8 = 0.125, 1/4 = 0.25, 1/2 = 0.5, 3/4 = 0.75 (so 67 3/4 in = 67.75 in)
Area units (Grades 3–5)	The area of a rectangle is length × width 1 ft² = 12 in × 12 in = 144 in², so dividing square inches by 144 gives square feet
Rounding (Grade 4)	The difference between rounding up, rounding down and rounding to the nearest Being able to explain in your own words why an inside mount rounds down and an outside mount rounds up
Unit price and quantity (Grade 6)	A unit price times a quantity gives the cost, as in "$6.50 per ft² × 22.47 ft²"

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 inside mount order size

Inside width (in)	68
Inside height (in)	48
Width deduction (total, in)	0.25
Height deduction (in)	0.25
Order width (in)	=B1-B3
Order height (in)	=B2-B4

Table to find the outside mount order size

Outside width (in)	72
Outside height (in)	52
Side overlap (each side, in)	1.5
Room at the top (in)	1.5
Overlap at the bottom (in)	1.5
Order width (in)	=B1+2*B3
Order height (in)	=B2+B4+B5

Table to find the area and estimated cost

Order width (in)	67.75
Order height (in)	47.75
Price per ft² ($)	6.50
Area (ft²)	=B1*B2/144
Estimated cost ($)	=ROUND(B3*B4,2)

After pasting, the upper rows of column B are the inputs and the last rows (and some middle rows) are calculated automatically.
The first table is the inside mount (inside size minus the deduction) and the second is the outside mount (outside size plus the overlaps). To round the order size to 1/8 in, use "=FLOOR(B1-B3,0.125)" (round down) for an inside mount and "=CEILING(B1+2*B3,0.125)" (round up) for an outside mount.
ROUND(value, 2) in the third table rounds to the cent. For several windows, place a copy of the third table for each window side by side and add up the areas and costs.
With the example numbers, B5 is 67.75 and B6 is 47.75 in the first table, B6 is 75 and B7 is 55 in the second, and B4 is about 22.4657 and B5 is 146.03 in the third. Just change column B to your own numbers.

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 inside mount order size

Inside width (in)	68
Inside height (in)	48
Width deduction (total, in)	0.25
Height deduction (in)	0.25
Order width (in)	=B1-B3
Order height (in)	=B2-B4

Table to find the outside mount order size

Outside width (in)	72
Outside height (in)	52
Side overlap (each side, in)	1.5
Room at the top (in)	1.5
Overlap at the bottom (in)	1.5
Order width (in)	=B1+2*B3
Order height (in)	=B2+B4+B5

Table to find the area and estimated cost

Order width (in)	67.75
Order height (in)	47.75
Price per ft² ($)	6.50
Area (ft²)	=B1*B2/144
Estimated cost ($)	=ROUND(B3*B4,2)

The same formulas as Excel (including ROUND, FLOOR and CEILING) work as is. Copy the whole table, paste it into cell A1 and change column B to your own numbers.

How to calculate it in Python

import math

mount = "inside"         # mount type (inside or outside)
width_in = 68            # window width (inside size for inside mount, outside size for outside mount, in)
height_in = 48           # window height (same, in)
deduct_width_in = 0.25   # inside mount: width deduction (total, in)
deduct_height_in = 0.25  # inside mount: height deduction (in)
overlap_side_in = 1.5    # outside mount: side overlap (each side, in)
overlap_top_in = 1.5     # outside mount: room at the top (in)
overlap_bottom_in = 1.5  # outside mount: overlap at the bottom (in)
round_unit_in = 0.125    # rounding step for the order size (0.125 = 1/8 in; 0 for no rounding)
price_per_ft2 = 6.50     # price per ft² ($; 0 if not needed)

if mount == "inside":
    order_width = width_in - deduct_width_in          # order width = inside size − deduction
    order_height = height_in - deduct_height_in       # order height = inside size − deduction
    if round_unit_in > 0:                             # inside mount rounds down to fit the frame
        order_width = math.floor(order_width / round_unit_in) * round_unit_in
        order_height = math.floor(order_height / round_unit_in) * round_unit_in
else:
    order_width = width_in + 2 * overlap_side_in      # order width = outside size + side overlap × 2
    order_height = height_in + overlap_top_in + overlap_bottom_in   # order height = outside size + top room + bottom overlap
    if round_unit_in > 0:                             # outside mount rounds up to cover the window
        order_width = math.ceil(order_width / round_unit_in) * round_unit_in
        order_height = math.ceil(order_height / round_unit_in) * round_unit_in

area_ft2 = order_width * order_height / 144           # area (ft²)
cost = price_per_ft2 * area_ft2                       # estimated cost ($)

print(f"Order width: {order_width} in, order height: {order_height} in")
print(f"Area: {area_ft2:.4f} ft²")
print(f"Estimated cost: ${cost:,.2f}")

It runs with the standard library only. math.floor() rounds down and math.ceil() rounds up. Change mount at the top to "outside" for an outside mount. For several windows, repeat the calculation for each window and add up area_ft2 and cost.

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

Inside mount order size (inside size minus the deduction)

W = w − a,  H = h − b

W = w - a,\quad H = h - b

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>W</mi><mo>=</mo><mi>w</mi><mo>-</mo><mi>a</mi>
    <mo>,</mo>
    <mi>H</mi><mo>=</mo><mi>h</mi><mo>-</mo><mi>b</mi>
  </mrow>
</math>

W = w - a,  H = h - b

W = w - a; H = h - b

W := w - a;  H := h - b;

W = w - a; H = h - b;

W = w − a, H = h − b

Outside mount order size (outside size plus the overlaps)

W = w + 2c,  H = h + t + d

W = w + 2c,\quad H = h + t + d

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>W</mi><mo>=</mo><mi>w</mi><mo>+</mo><mn>2</mn><mo>&#x2062;</mo><mi>c</mi>
    <mo>,</mo>
    <mi>H</mi><mo>=</mo><mi>h</mi><mo>+</mo><mi>t</mi><mo>+</mo><mi>d</mi>
  </mrow>
</math>

W = w + 2 c,  H = h + t + d

W = w + 2*c; H = h + t + d

W := w + 2*c;  H := h + t + d;

W = w + 2*c; H = h + t + d;

W = w + 2c, H = h + t + d

Area and estimated cost

A = W × H ÷ 144,  T = u × A

A = \frac{W H}{144},\quad T = u A

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>A</mi><mo>=</mo>
    <mfrac><mrow><mi>W</mi><mo>&#x2062;</mo><mi>H</mi></mrow><mn>144</mn></mfrac>
    <mo>,</mo>
    <mi>T</mi><mo>=</mo><mi>u</mi><mo>&#x2062;</mo><mi>A</mi>
  </mrow>
</math>

A = (W H) / 144,  T = u A

A = W*H/144; T = u*A

A := W*H/144;  T := u*A;

A = W*H/144; T = u*A;

A = W H/144, T = u A

How to have ChatGPT do the calculation

You are an assistant for measuring blinds and shades. Do the calculations below by actually running Python code, and base your answer only on the numbers from the output (do not calculate in your head or guess).

There are two windows. Window 1 has an inside size of 68 in wide and 48 in high, and window 2 has an inside size of 36 in wide and 44 in high. I am ordering inside-mount horizontal blinds for both.
Use a width deduction of 1/4 in (total) and a height deduction of 1/4 in, and round the order size down to the nearest 1/8 in. The price is $6.50 per square foot.
Find each of the following.
1. The order width and order height of windows 1 and 2 (inside size − deduction)
2. The area of windows 1 and 2 (order width × order height ÷ 144, in ft²) and the total area
3. The total estimated cost (price per ft² × total area, rounded to the cent)

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\(w\)	lowercase double-u	The window width. Measure the inside width for an inside mount and the outside width for an outside mount. It comes from "width", and it is lowercase to tell it apart from the order width \(W\).
\(h\)	lowercase aitch	The window height - the inside height for an inside mount and the outside height for an outside mount. It comes from "height".
\(a\)	ay	The width deduction for an inside mount (both sides together). About 1/4 in is common. Think of it as "allowance".
\(b\)	bee	The height deduction for an inside mount (at the bottom). About 1/4 in is common, and about 1/2 in for vertical blinds. Think of it as "bottom".
\(W\)	capital double-u	The order width (the product width). It is \(W = w - a\) for an inside mount and \(W = w + 2c\) for an outside mount.
\(H\)	capital aitch	The order height (the product height). It is \(H = h - b\) for an inside mount and \(H = h + t + d\) for an outside mount.
\(c\)	cee	The side overlap for an outside mount (each side). There are two sides, so add it twice. About 1.5 in per side is common. Think of it as "cover".
\(t\)	tee	The room at the top for an outside mount, for the brackets and headrail above the frame. About 1.5 in is common. It comes from "top".
\(d\)	dee	The overlap at the bottom for an outside mount, how far it hangs below the frame. About 1.5 in is common. Think of it as "down".
\(A\)	capital ay	The product area (ft²). It is found with \(A = W \times H \div 144\). It comes from "area".
\(u\)	you	The price per ft² ($ per square foot of product). It comes from "unit price".
\(p\)	pee	The price per window (for that window's product). With three windows, they are numbered \(p_1, p_2, p_3\). It comes from "price".
\(T\)	capital tee	The total estimated cost. It is \(T = u \times A\) with a price per ft², or \(T = p_1 + p_2 + p_3\) with prices per window. It comes from "total".
\(\mathrm{ft^2}\)	square feet	A unit of area: a square 1 ft on each side, also written sq ft. \(1\,\mathrm{ft^2} = 144\,\mathrm{in^2}\) (and \(1\,\mathrm{m^2} \approx 10.76\,\mathrm{ft^2}\)).

Blind and Shade Size Calculator (Inside and Outside Mount)

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