Choose a method and enter the building dimensions (measurement method) or the total floor area (quick estimate). Gables, openings and price can be left blank (those items are then skipped).
Gable width (m)
Gable height (m)
Count
Width (m)
Height (m)
Count
All lengths are in meters (m). Divide values measured in cm by 100 before entering them (for example, a wall height of 580 cm → 5.8).
Result and figure
Enter the building dimensions (or the total floor area) on the left and press "Calculate". The result will appear here.
Table of Contents
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What you can do on this page
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What is this calculation used for?
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How to Use
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Formulas and figures
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Symbols and terms
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Good to know before you start
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How to calculate it in Excel
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How to calculate it in Google Sheets
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How to calculate it in Python
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How to write it in LaTeX and other math languages (copy and paste)
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How to have ChatGPT do the calculation
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DataChef Features
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Related Features
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NumberChef Calculators List
What you can do on this page
- Enter the building perimeter (or length × width) and the wall height, and you get the paintable area used for painting and siding estimates on the spot (measurement method)
- Enter windows, doors and other openings as "width × height × count" in up to 6 rows, and their total area is subtracted automatically (you can also enter the total directly)
- It also handles common estimating tasks, such as adding the triangular gable walls of a gable roof and making a quick estimate from the total floor area × a factor (quick estimate)
- Enter a price per square foot, and the estimated cost is calculated from the paintable area too (the price can be left blank)
- A plain-language explanation of the formulas and copy-and-paste formulas for Excel, Google Sheets and Python are all on this page
The measurement method treats the walls as one rectangle, "perimeter × wall height", as if they were unfolded flat. The real area goes up or down with an irregular outline and with the roof shape (gables, parapets and so on). The quick estimate is only a rough guide, and its factor changes with the building shape. For a formal estimate, check quantities based on drawings or measurements. For the interior walls and ceiling of a room, use the "Room Wall, Ceiling and Floor Area Calculator".
What is this calculation used for?
Checking the quantity on an exterior painting estimate
An exterior painting estimate lists the wall area in square feet and a price. That square footage is the paintable area, which the contractor takes off from drawings or measurements as "perimeter × wall height − openings".
For example, with a 140 ft perimeter, an 18 ft wall height and 159 ft² of openings, the paintable area is \(2520 - 159 = 2361\) ft². If the estimate's quantity is very different (for example, the same number as the floor area, or openings not subtracted), that is a good reason to ask how it was measured. Prices per square foot vary a lot with the paint quality, so even checking the quantity makes estimates easier to compare.
Material for new siding
When you replace siding, or install new siding over the old walls, the paintable area is the area to be covered. In the US, siding is ordered by the "square" (100 ft²), and adding about 10% for cuts and offcuts is common. For 2,361 ft², that is \(2361 \times 1.1 = 2597.1\) ft², or 26 squares after rounding up.
Finding the number of pieces, boxes and the cost from an area works the same way as the "Tile Calculator".
How many gallons to paint a shed yourself
Many people paint small buildings such as sheds, garages and workshops themselves. The paint can says how many square feet one gallon covers per coat, so once you know the paintable area, you know how much paint to buy.
For example, a 10 ft × 8 ft shed with 8 ft walls has a 36 ft perimeter and 288 ft² of wall. Subtracting a 4 ft × 6 ft door and two 2 ft × 2 ft windows leaves \(288 - 24 - 8 = 256\) ft². With two coats and 350 ft² per gallon, you need \(256 \times 2 \div 350 \approx 1.46\), so 2 gallons. Follow the manufacturer's instructions for the number of coats.
A rough estimate for a house without drawings (quick estimate)
When you are thinking about buying an older house, or helping your parents plan a remodel, you often have no drawings and cannot measure yet, but you do know the square footage. For a two-story house of 1,800 ft², a factor of 1.2 gives a paintable area of about \(1800 \times 1.2 = 2160\) ft², and a factor of 1.4 gives about 2,520 ft².
Keeping this range in mind gives you a feel for the size of the job before you talk to a contractor. For a formal estimate, check the quantity with the measurement method.
Quantity takeoff in construction estimating
In construction estimating (counting the materials and labor a job needs from the drawings), the basic step for exterior finishes is to take off "perimeter × total story height − openings". The measurement method on this page turns that idea directly into a formula.
In practice, estimators take off each story and each side separately, add parapets (the low walls around a flat roof) and gables, and agree with the client on rules for deducting openings (for example, small openings are not subtracted).
Formulas and figures
Building perimeter
Figure
Standard notation
(the usual math form)
\(L\)
\(=\)
\(2\)
\(\times\)
\((\)
\(a\)
\(+\)
\(b\)
\()\)
In words
(symbols replaced with words)
③
\(L\): building perimeter
\(=\)
\(2\)
\(\times\)
\((\)
①
\(a\): building length
\(+\)
②
\(b\): building width
\()\)
The formula in words
①
Add the
\(a\): building length
②
and the
\(b\): building width
and double it (the distance around a rectangle)
③
to get the
\(L\): building perimeter
Quick example
The perimeter of a house with a 40 ft × 30 ft rectangular outline is
\(L\): perimeter
\(=\)
\(2\)
\(\times\)
\((\)
length (40 ft)
\(+\)
width (30 ft)
\()\)
\(2 \times (40 + 30) = 2 \times 70 = 140\,\mathrm{ft}\)
Key idea
The perimeter is the distance once around the building. If you cut the walls open and spread them flat like a sheet of paper (an unfolded view, or net), you get a rectangle whose width is the perimeter and whose height is the wall height. The area of this rectangle is the gross wall area found with the next formula.
For a building that is not a rectangle (an L-shaped house or one with bump-outs), do not use this formula. Add up the lengths of all sides once around and enter the total under "Enter the perimeter". The walls of recessed parts are painted too, so the perimeter is longer than for a rectangular house.
Gross wall area (before openings)
Figure
Standard notation
(the usual math form)
\(A_{0}\)
\(=\)
\(L\)
\(\times\)
\(h\)
In words
(symbols replaced with words)
③
\(A_{0}\): gross wall area
\(=\)
①
\(L\): building perimeter
\(\times\)
②
\(h\): wall height
The formula in words
①
Multiply the
\(L\): building perimeter
②
by the
\(h\): wall height
(the area of the unfolded rectangle)
③
to get the
\(A_{0}\): gross wall area
Quick example
The gross wall area of a house with a 140 ft perimeter and an 18 ft wall height is
\(A_{0}\): gross area
\(=\)
perimeter (140 ft)
\(\times\)
wall height (18 ft)
\(140 \times 18 = 2520\,\mathrm{ft^2}\)
Key idea
The wall height here is the height from the top of the foundation to the eaves (the lower edge of the roof). A height taken from the ground adds the foundation to the area. Exposed concrete foundation is usually not painted or sided, so subtract its height, or measure from the top of the foundation.
A house with a gable roof has triangular walls, called gables, at the ends where you see the roof slope; they rise above the eaves. Gables are not part of the unfolded rectangle, so if needed add the triangle area \(\dfrac{\text{width} \times \text{height}}{2}\) for each gable (2 for both ends). For a 30 ft wide end with a 6/12 roof pitch, the gable height is 7.5 ft, so two gables add \(30 \times 7.5 \div 2 \times 2 = 225\) ft². Enter the width and height under "Gables" in the calculator and this amount \(G\) is added automatically.
Total area of openings (windows and doors)
Standard notation
(the usual math form)
\(O\)
\(=\)
\(\sum\)
\((\)
\(w_{i}\)
\(\times\)
\(h_{i}\)
\(\times\)
\(n_{i}\)
\()\)
In words
(symbols replaced with words)
④
\(O\): total area of openings
\(=\)
\(\sum\)
\((\)
①
\(w_{i}\): opening width
\(\times\)
②
\(h_{i}\): opening height
\(\times\)
③
\(n_{i}\): count of that size
\()\)
The formula in words
①
Multiply the
\(w_{i}\): opening width
②
by the
\(h_{i}\): opening height
to get the area of one opening,
③
multiply by the
\(n_{i}\): count of that size
and add this up for every size (the symbol \(\sum\) means "add them all")
④
to get the
\(O\): total area of openings
Quick example
For a house with eight 3 ft × 5 ft windows, one 3 ft × 7 ft front door and three 2 ft × 3 ft small windows, the total area of openings is
\(3 \times 5 \times 8 = 120\)
\(3 \times 7 \times 1 = 21\)
\(2 \times 3 \times 3 = 18\)
\(120 + 21 + 18 = 159\,\mathrm{ft^2}\)
Key idea
Windows, doors, garage doors, vents and other parts that are not wall are not painted or sided, so they are subtracted from the gross area. Putting windows of the same size in one row and multiplying by the count makes entry easier.
You do not need to subtract every small vent or pipe hole. In practice, estimators often subtract only the large windows and doors, and leave small openings in because cutting in around them takes extra time anyway. How much to subtract depends on what is agreed for the estimate.
Paintable area (measurement method)
Figure
Standard notation
(the usual math form)
\(S\)
\(=\)
\(A_{0}\)
\(+\)
\(G\)
\(-\)
\(O\)
In words
(symbols replaced with words)
④
\(S\): paintable area
\(=\)
①
\(A_{0}\): gross wall area
\(+\)
②
\(G\): gable area
\(-\)
③
\(O\): total area of openings
The formula in words
①
Take the
\(A_{0}\): gross wall area
②
add the
\(G\): gable area
(0 if there are no gables),
③
subtract the
\(O\): total area of openings
④
and you get the
\(S\): paintable area
Quick example
For a house with a gross area of 2,520 ft², no gables and 159 ft² of openings, the paintable area is
\(S\): paintable area
\(=\)
gross area (2,520 ft²)
\(+\)
gables (0 ft²)
\(-\)
openings (159 ft²)
\(2520 + 0 - 159 = 2361\,\mathrm{ft^2}\)
Key idea
The paintable area is the area you actually paint (or cover with siding). How much paint and how many gallons you need, and estimates priced per square foot, are all based on this area.
In the unfolded view, take the perimeter × wall height rectangle (the gross area), add the gable triangles and cut out the window and door rectangles: what is left is the paintable area. If the openings add up to the gross area or more, a unit was probably mixed up somewhere (such as inches and feet), so check the entries.
This calculation treats the walls as flat surfaces. Deeply textured siding and trim items such as soffits (the underside of the eaves), fascia and gutters are usually measured separately.
Estimated paintable area (quick estimate)
Standard notation
(the usual math form)
In words
(symbols replaced with words)
\(S\)
\(\approx\)
\(F\)
\(\times\)
\(k\)
③
\(S\): estimated paintable area
\(\approx\)
①
\(F\): total floor area
\(\times\)
②
\(k\): factor
The formula in words
①
Multiply the
\(F\): total floor area
②
by the
\(k\): factor (the rough ratio of wall area to floor area)
③
to get the
\(S\): estimated paintable area
Quick example
For a two-story house with a total floor area of 2,000 ft² and a factor of 1.2, the estimate is
\(S\): estimated paintable area
\(\approx\)
total floor area (2,000 ft²)
\(\times\)
factor (1.2)
\(2000 \times 1.2 = 2400\,\mathrm{ft^2}\)
Key idea
The factor \(k\) is the ratio "how many times the floor area the wall area is". To see why the floor area can predict the wall area, think of a square house. For a two-story house with square floors \(a\) ft on each side and 9 ft per story (18 ft in total), the total floor area is \(2a^{2}\) and the gross wall area is \(4a \times 18 = 72a\), so the ratio is \(\dfrac{72a}{2a^{2}} = \dfrac{36}{a}\). For 30 ft sides it is 1.2, for 24 ft sides 1.5, and for 40 ft sides 0.9. (This is before openings are subtracted, so the factor for the paintable area is a little smaller.)
So the factor changes with the size and shape of the building, the story height and the number of openings. It is larger for small, narrow or irregular houses and smaller for large ones. This calculator uses 1.2 as the default, but that is only one rough guide. Try a couple of factors, such as 1.0 and 1.4, to see the range; then a real estimate will not surprise you. If you know the dimensions from drawings or measurements, use the measurement method instead.
Estimated cost
Standard notation
(the usual math form)
In words
(symbols replaced with words)
\(T\)
\(=\)
\(u\)
\(\times\)
\(S\)
③
\(T\): estimated cost
\(=\)
①
\(u\): unit price
\(\times\)
②
\(S\): paintable area
The formula in words
①
Multiply the
\(u\): unit price (per square foot of paintable area)
②
by the
\(S\): paintable area
③
to get the
\(T\): estimated cost
Quick example
The cost of painting 2,361 ft² at $2.50 per square foot is
\(T\): estimated cost
\(=\)
unit price ($2.50)
\(\times\)
paintable area (2,361 ft²)
\(2.50 \times 2361 = 5902.50\)
Key idea
The key is to price everything "per square foot of paintable area". A painting estimate usually multiplies a price per square foot (which depends on the paint quality) by the paintable area, and then adds separate items such as pressure washing, masking, surface repair, trim (soffits, fascia, gutters) and sometimes scaffolding or lifts. This formula covers only the walls themselves, so use it as a check of "wall quantity × price", not as an estimate of the total.
The basic way to find the paintable exterior wall area is "perimeter × wall height (+ gables) − openings" (the measurement method). Without drawings, you can make a rough estimate with "total floor area × a factor" (the quick estimate; the factor depends on the size of the house). Paint quantities and prices per square foot are based on this paintable area.
Symbols and terms
Symbols
| \(a\) | ay | The building length (depth, ft). Used to find the perimeter of a building with a rectangular outline. |
| \(b\) | bee | The building width (front, ft). It does not matter which side is the length and which is the width. |
| \(L\) | ell | The building perimeter (ft). \(L\) is the first letter of "length". For a rectangle \(L = 2(a + b)\); for other shapes, add up all sides once around. |
| \(h\) | aitch | The wall height (ft), from the top of the foundation to the eaves (the lower edge of the roof). \(h\) is the first letter of "height". |
| \(A_{0}\) | ay sub zero | The gross wall area (before openings, ft²). \(A\) is the first letter of "area", and the subscript 0 means "the original area, before subtracting". Found with \(A_{0} = L \times h\). |
| \(G\) | gee | The gable area (the triangles of a gable roof, ft²). \(G\) is the first letter of "gable". It is width \(\times\) height \(\div 2\) for each gable, added together, and 0 if there are no gables. |
| \(w_{i}\), \(h_{i}\), \(n_{i}\) | double-u sub i, aitch sub i, en sub i | The width (ft), height (ft) and count of the \(i\)-th kind of opening. The subscript \(i\) is the row number; windows of the same size go in one row. |
| \(O\) | oh | The total area of openings (windows and doors, ft²). \(O\) is the first letter of "opening". Found with \(O = \sum w_{i} h_{i} n_{i}\). |
| \(\sum\) | sigma | The symbol for "add them all up". It is the Greek letter sigma, which matches S for "sum". \(\sum_{i} w_{i} h_{i} n_{i}\) means "add the areas of row 1, row 2 and so on". |
| \(S\) | ess | The paintable area (wall area, ft²). \(S\) is the first letter of "surface". It is \(S = A_{0} + G - O\) with the measurement method and \(S \approx F \times k\) with the quick estimate. |
| \(F\) | ef | The total floor area (ft²; m² in metric mode). \(F\) is the first letter of "floor". |
| \(k\) | kay | The factor for the quick estimate, the rough ratio of wall area to floor area. It changes with the size and shape of the building and the number of openings (this calculator's default is 1.2). |
| \(u\) | you | The unit price ($/ft²), the price per square foot of paintable area. \(u\) is the first letter of "unit price". |
| \(T\) | tee | The estimated cost ($). \(T\) is the first letter of "total". Found with \(T = u \times S\). |
| \(\approx\) | approximately equal to | The symbol for "approximately equal". The quick estimate is only approximate, so its formula uses this symbol instead of the equals sign (=). |
Terms
| perimeter | The distance once around the building. It is the width of the unfolded view of the walls. For an L-shaped or irregular house, add up every side, including the walls of recessed parts. |
| wall height | The height from the top of the foundation to the eaves (the lower edge of the roof), which is the height of the area to be painted. A height measured from the ground includes the exposed foundation, so subtract that part. A two-story house is often about 17–20 ft. |
| opening | A window, door, garage door, vent or other gap in the wall. It is not painted or sided, so its area is subtracted from the wall area. An estimate may list this as a deduction for openings. |
| gable | The triangular wall at the end of a building with a gable roof, where you see the roof slope. It rises above the eaves, so it is not part of the "perimeter × wall height" rectangle; add the triangle areas separately if needed. |
| gable roof | A roof that slopes in two directions, like an open book placed face down, and one of the most common roof shapes. It has a gable at each end. A hip roof, which slopes in four directions, has no gables. |
| paintable area | The area actually painted or sided. It is the gross wall area minus the openings. The paint needed (area × number of coats ÷ coverage per gallon) and prices per square foot are based on this area. |
| total floor area | The floor areas of all stories added together, as shown on floor plans and property listings. The quick estimate multiplies this area by a factor to estimate the wall area. |
| measurement method | Finding the area from measured dimensions (or from drawings) as perimeter × wall height minus openings. It is the basic way to estimate and more accurate than the quick estimate. |
| quick estimate | Estimating the wall area roughly by multiplying the total floor area by a factor. Use it as a guide when you have no drawings or measurements. |
| net | A drawing of the surface of a solid cut open and laid flat (an unfolded view). Unfolding the walls of a building gives a rectangle whose width is the perimeter and whose height is the wall height. |
| trim | Painted parts other than the walls themselves, such as soffits (the underside of the eaves), fascia (the boards along the roof edge), gutters, shutters and window and door casings. Estimates usually measure them separately from the walls. |
| siding | Exterior wall cladding made of boards or panels, such as vinyl, fiber cement, wood or metal. For new siding, the amount needed is found from the same wall area as the paintable area. In the US, siding is usually ordered by the "square" (100 ft²). |
| quantity takeoff | Counting the amounts of material and labor a job needs from drawings or measurements, and pricing them. Taking off the wall area as "perimeter × wall height − openings" is one of its basic steps. |
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.
| Perimeter and area of a rectangle (Grades 3–4) |
|
| Area of a triangle (Grade 6) |
|
| Nets of a rectangular prism (Grade 6) |
|
| Converting units of length and area (Grades 4–5) |
|
| Decimal multiplication and ratios (Grades 5–6) |
|
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 building perimeter
| Building length (ft) | 40 |
| Building width (ft) | 30 |
| Building perimeter (ft) | =2*(B1+B2) |
Table to find the gross wall area
| Building perimeter (ft) | 140 |
| Wall height (ft) | 18 |
| Gross wall area (ft²) | =B1*B2 |
Table to find the total area of openings
| Opening 1: width × height × count (ft²) | =3*5*8 |
| Opening 2: width × height × count (ft²) | =3*7*1 |
| Opening 3: width × height × count (ft²) | =2*3*3 |
| Total area of openings (ft²) | =SUM(B1:B3) |
Table to find the paintable area (measurement method)
| Gross wall area (ft²) | 2520 |
| Gable area (ft²) | 0 |
| Total area of openings (ft²) | 159 |
| Paintable area (ft²) | =B1+B2-B3 |
Table to estimate the paintable area (quick estimate)
| Total floor area (ft²) | 2000 |
| Factor | 1.2 |
| Estimated paintable area (ft²) | =B1*B2 |
Table to find the estimated cost
| Unit price ($/ft²) | 2.5 |
| Paintable area (ft²) | 2361 |
| Estimated cost ($) | =B1*B2 |
After pasting, the upper cells in column B are your inputs and the last row is calculated automatically.
B3 of the first table is 140, B3 of the second table is 2520, the rows of the third table are 120, 21 and 18 with B4 = 159, B4 of the fourth table is 2361, B3 of the fifth table is 2400, and B3 of the sixth table is 5902.5.
To add more openings to the third table, insert rows and widen the range in "SUM(B1:B3)". Just replace the numbers in column B with your own.
B3 of the first table is 140, B3 of the second table is 2520, the rows of the third table are 120, 21 and 18 with B4 = 159, B4 of the fourth table is 2361, B3 of the fifth table is 2400, and B3 of the sixth table is 5902.5.
To add more openings to the third table, insert rows and widen the range in "SUM(B1:B3)". 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 building perimeter
| Building length (ft) | 40 |
| Building width (ft) | 30 |
| Building perimeter (ft) | =2*(B1+B2) |
Table to find the gross wall area
| Building perimeter (ft) | 140 |
| Wall height (ft) | 18 |
| Gross wall area (ft²) | =B1*B2 |
Table to find the total area of openings
| Opening 1: width × height × count (ft²) | =3*5*8 |
| Opening 2: width × height × count (ft²) | =3*7*1 |
| Opening 3: width × height × count (ft²) | =2*3*3 |
| Total area of openings (ft²) | =SUM(B1:B3) |
Table to find the paintable area (measurement method)
| Gross wall area (ft²) | 2520 |
| Gable area (ft²) | 0 |
| Total area of openings (ft²) | 159 |
| Paintable area (ft²) | =B1+B2-B3 |
Table to estimate the paintable area (quick estimate)
| Total floor area (ft²) | 2000 |
| Factor | 1.2 |
| Estimated paintable area (ft²) | =B1*B2 |
Table to find the estimated cost
| Unit price ($/ft²) | 2.5 |
| Paintable area (ft²) | 2361 |
| Estimated cost ($) | =B1*B2 |
The same formulas as in Excel (including the SUM function) 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
building_length_ft = 40 # building length (depth, ft)
building_width_ft = 30 # building width (front, ft)
wall_height_ft = 18 # wall height (top of foundation to eaves, ft)
gable_area_ft2 = 0 # gable area (ft²). For a gable roof: width * height / 2 * count
openings = [ # openings (width ft, height ft, count). Put the same size in one row
(3, 5, 8), # windows
(3, 7, 1), # front door
(2, 3, 3), # small windows
]
unit_price_usd = 2.50 # unit price ($/ft²)
perimeter_ft = 2 * (building_length_ft + building_width_ft) # building perimeter
gross_area_ft2 = perimeter_ft * wall_height_ft # gross wall area (before openings)
opening_area_ft2 = sum(w * h * n for (w, h, n) in openings) # total area of openings
paint_area_ft2 = gross_area_ft2 + gable_area_ft2 - opening_area_ft2 # paintable area (measurement method)
cost_usd = unit_price_usd * paint_area_ft2 # estimated cost
# quick estimate (total floor area x factor)
floor_area_ft2 = 2000
factor = 1.2
paint_area_quick_ft2 = floor_area_ft2 * factor
print(f"Building perimeter: {perimeter_ft} ft")
print(f"Gross wall area: {gross_area_ft2} ft²")
print(f"Total area of openings: {opening_area_ft2:.2f} ft²")
print(f"Paintable area (measurement method): {paint_area_ft2:.2f} ft²")
print(f"Estimated cost: ${cost_usd:,.2f}")
print(f"Estimated paintable area (quick estimate): {paint_area_quick_ft2:.2f} ft²")
Runs with the standard library only. Change the tuples in openings to the windows and doors of your own house, change the sizes and the price, and run it. sum() is the ∑ (add them all) in the formula.
How to write it in LaTeX and other math languages (copy and paste)
Building perimeter
L = 2 × (a + b)
L = 2(a + b)
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>L</mi>
<mo>=</mo>
<mn>2</mn>
<mo>⁢</mo>
<mrow><mo>(</mo><mi>a</mi><mo>+</mo><mi>b</mi><mo>)</mo></mrow>
</mrow>
</math>
L = 2(a + b)
2*(a + b)
L := 2*(a + b);
L = 2*(a + b);
L = 2(a + b)
Gross wall area (before openings)
A₀ = L × h
A_{0} = L \times h
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<msub><mi>A</mi><mn>0</mn></msub>
<mo>=</mo>
<mi>L</mi>
<mo>×</mo>
<mi>h</mi>
</mrow>
</math>
A_0 = L xx h
l*h
A0 := L*h;
A0 = L*h;
A_0 = L × h
Total area of openings (windows and doors)
O = Σ (wᵢ × hᵢ × nᵢ)
O = \sum_{i} w_{i} h_{i} n_{i}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>O</mi>
<mo>=</mo>
<munder><mo>∑</mo><mi>i</mi></munder>
<msub><mi>w</mi><mi>i</mi></msub>
<mo>⁢</mo>
<msub><mi>h</mi><mi>i</mi></msub>
<mo>⁢</mo>
<msub><mi>n</mi><mi>i</mi></msub>
</mrow>
</math>
O = sum_i w_i h_i n_i
Total[w*h*n]
Op := add(w[i]*h[i]*n[i], i = 1 .. k);
O = sum(w.*h.*n);
O = ∑_i w_i h_i n_i
Paintable area (measurement method)
S = A₀ + G − O
S = A_{0} + G - O
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>S</mi>
<mo>=</mo>
<msub><mi>A</mi><mn>0</mn></msub>
<mo>+</mo>
<mi>G</mi>
<mo>−</mo>
<mi>O</mi>
</mrow>
</math>
S = A_0 + G - O
a0 + g - o
S := A0 + G - Op;
S = A0 + G - O;
S = A_0 + G − O
Estimated paintable area (quick estimate)
S ≈ F × k
S \approx F \times k
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>S</mi>
<mo>≈</mo>
<mi>F</mi>
<mo>×</mo>
<mi>k</mi>
</mrow>
</math>
S ~~ F xx k
f*k
S := F*k;
S = F*k;
S ≈ F × k
Estimated cost
T = u × S
T = u \times S
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>T</mi>
<mo>=</mo>
<mi>u</mi>
<mo>×</mo>
<mi>S</mi>
</mrow>
</math>
T = u * S
u*s
T := u*S;
T = u*S;
T = u × S
How to have ChatGPT do the calculation
You are a quantity calculation assistant for exterior painting. 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). A two-story house has a 40 ft × 30 ft rectangular outline and a wall height (from the top of the foundation to the eaves) of 18 ft. There are no gables. The openings are eight 3 ft × 5 ft windows, one 3 ft × 7 ft front door and three 2 ft × 3 ft small windows. Find each of the following: 1. The building perimeter (ft) 2. The gross wall area (perimeter × wall height, ft²) 3. The total area of openings (ft²) 4. The paintable area (gross area − openings, ft²) 5. The estimated cost at $2.50 per square foot of paintable area ($) 6. For reference, the paintable area estimated with the quick method as total floor area 2,400 ft² × factor 1.2 (ft²), and its difference from the result of 4 Show the formulas you used and the numbers from the execution result.
How to Use
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1Enter your numbersType the numbers you want to calculate with into the input fields
-
2CalculatePress the "Calculate" button
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3Check the resultThe result appears on the spot. The same page also explains the idea behind the calculation and the formula
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