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AnswerFloor area and exterior wall area are different measurementsOpenings, coats and the calculator fieldsUse the coverage on the can, and expect less on a rough surfaceSquare metres and litresWorked example — 2,000 sq ft, two storeys, two coats at 250 ft² per gallon
The example footprint is 40 × 25 ft, which is 1,000 ft², half of 2,000. Perimeter is 2 × (40 + 25) = 130 ft. Wall height is 18 ft, so gross wall area is 130 × 18 = 2,340 ft². Two doors at 20 ft² and 13 windows at 15 ft² are 40 + 195 = 235 ft². Net wall area is 2,340 − 235 = 2,105 ft². Two coats are 2,105 × 2 = 4,210 ft² of film. At 250 ft² per gallon, 4,210 ÷ 250 = 16.84, which rounds up to 17 US gallons. The one-storey 50 × 40 ft plan is 1,310 ft² net, and 1,310 × 2 ÷ 250 = 10.48, which rounds up to 11.
| Floor area | Plan | Net ft² | 1 coat | 2 coats |
|---|---|---|---|---|
| 1,000 sq ft | 40 × 25 ft | 935 | 4 | 8 |
| 1,500 sq ft | 50 × 30 ft | 1,160 | 5 | 10 |
| 2,000 sq ft | 50 × 40 ft | 1,310 | 6 | 11 |
| 2,500 sq ft | 50 × 50 ft | 1,460 | 6 | 12 |
| 3,000 sq ft | 60 × 50 ft | 1,610 | 7 | 13 |
| Floor area | Plan | Net ft² | 1 coat | 2 coats |
|---|---|---|---|---|
| 1,000 sq ft | 25 × 20 ft | 1,445 | 6 | 12 |
| 1,500 sq ft | 30 × 25 ft | 1,775 | 8 | 15 |
| 2,000 sq ft | 40 × 25 ft | 2,105 | 9 | 17 |
| 2,500 sq ft | 50 × 25 ft | 2,435 | 10 | 20 |
| 3,000 sq ft | 50 × 30 ft | 2,600 | 11 | 21 |
Painting calculator
Exterior paint calculator
Exterior-paint gallons from wall length, height, openings, coats and labelled coverage. Interior rooms use the paint calculator.
By Feroz Sheikh · Formula PAINT-EXT-001 v1.0.0 · Tested formula
PAINT-EXT-001v1.0.0Project inputs
Enter your measurements. Switching units converts the same project, including coverage and unit rates. Package yields keep the unit printed beside each field.
Calculated result
Exterior paint gallons
PAINT-EXT-001(wall length × height − openings) × coats × (1 + waste) ÷ coverage
Gross wall area
Paintable area
Area across coats + waste
Planning estimate, not engineering advice. Confirm site measurements and product specifications. Calculation limits.
Exterior wall length times height, minus door and window openings, times coats, divided by labelled exterior coverage after waste.
- Measure each elevation. Measure gables separately as base × vertical height ÷ 2. On a separate takeoff, enter half the base as wall length, the gable height and measured openings; keep waste separate.
- Exterior coverage is not interior coverage. Use the can you will roll outside.
- Trim paint is the trim calculator.
Add your project costs
Enter supplier prices and any labour, equipment or delivery costs. Pick a currency — badges, inputs, and totals follow.
Costs use the can rate you type. Construclytic does not fetch paint prices. Primer, ceiling gallons and cut-and-roll labour stay on their own lines. For GCC projects, select QAR, AED, SAR, KWD, OMR or BHD and enter local supplier rates.
Floor area and exterior wall area are different measurements
The number in a listing is floor area. Exterior paint covers the walls. Behr’s exterior how-to, opened 27 October 2026, estimates the body by measuring the perimeter, then the height from the foundation to the roofline excluding gables, and multiplying those two figures. A more accurate estimate subtracts doors and windows. An average window on that page is 15 square feet and an average door is 20 square feet.
A one-storey row uses the floor area as the footprint and a 9 ft wall, the same eave height the exterior paint calculator starts with. A two-storey row splits the floor area in half for the footprint and uses 18 ft, two of those storeys, with no gable above the eave. A 2,000 sq ft one-storey plan of 50 × 40 ft has 1,310 ft² of net wall. The two-storey 40 × 25 ft plan has 2,105 ft². The same floor area produces two different paint quantities.
These rectangles are examples with exact areas. A longer, narrower house with the same floor area has a longer perimeter and more wall. Measure the building you are painting, then enter that perimeter as wall length. The elevation method, including a gable as base × vertical height ÷ 2, stays in how to estimate exterior paint.
Openings, coats and the calculator fields
Every row uses two doors and one 15 ft² window for every 10 ft of perimeter. The perimeters are multiples of 10, so the window count is an integer: 18 windows on the 180 ft one-storey 2,000 sq ft plan, and 13 windows on the 130 ft two-storey plan. Openings come out once. Coats multiply the net wall after that.
The exterior paint calculator rounds up with the formula (wall length × height − openings) × coats × (1 + waste) ÷ coverage. To reproduce the 2,000 sq ft two-storey row, enter length 130, height 18, doors 2, windows 13, door deduction 20, window deduction 15, coats 2, coverage 250 and waste 0. The tool opens with a 21 ft² door and 10% waste. With waste left at 10%, 16.84 × 1.10 = 18.524, which rounds up to 19 US gallons.
Sherwin-Williams Duration Exterior Acrylic Flat K32, data sheet marked 3/2026 and opened 27 October 2026, says to apply one coat on repaint work and two coats on bare surfaces. The 1-coat and 2-coat columns are those two cases at the same coverage. A separate primer, when the product system calls for one, is another container with its own coverage.
Use the coverage on the can, and expect less on a rough surface
Behr Premium Plus Exterior Flat No. 4050, technical data sheet marked 10/25 and opened 27 October 2026, lists 250 sq ft per gallon at 6.4 mils wet and 2.5 mils dry, and 400 sq ft per gallon at 4.0 mils wet and 1.6 mils dry. The sheet states coverage of 250–400 sq ft per gallon depending on application method and substrate porosity, and that this does not include the loss of material from spraying. It names stucco, brick, masonry, fiber cement and wood among the substrates. Behr’s how-to says one gallon of Behr paint covers 250 to 400 square feet with one coat, and that a porous, rough, textured or previously unpainted surface will generally require more paint.
Sherwin-Williams Duration Exterior Acrylic Flat K32 lists 250–300 sq ft per gallon at 5.3–6.4 mils wet and 2.2–2.7 mils dry. The surfaces named on that sheet include stucco, concrete, concrete block, cement composition siding and wood. Benjamin Moore Regal Select Exterior Flat 261, sheet marked 261 US 091426 and opened 27 October 2026, lists a spread rate of 300–400 sq ft per gallon and says the rate depends on surface texture and porosity. The 250 column is the shared low end of the Behr and Duration ranges. Duration’s high end of 300 sits between 250 and 400: the 2,000 sq ft two-storey film of 4,210 ft² ÷ 300 = 14.033…, which rounds up to 15 US gallons.
The table below repeats the same net walls at 400 sq ft per gallon, Behr’s thinner labelled film. Spraying loss is still outside both columns. Trim, gutters and soffits are a different area; the linear method is trim paint coverage. Interior ceilings stay in ceiling paint gallons.
| Floor area | Storeys | Net ft² | 1 coat | 2 coats |
|---|---|---|---|---|
| 1,000 sq ft | 1 | 935 | 3 | 5 |
| 1,500 sq ft | 1 | 1,160 | 3 | 6 |
| 2,000 sq ft | 1 | 1,310 | 4 | 7 |
| 2,500 sq ft | 1 | 1,460 | 4 | 8 |
| 3,000 sq ft | 1 | 1,610 | 5 | 9 |
| 1,000 sq ft | 2 | 1,445 | 4 | 8 |
| 1,500 sq ft | 2 | 1,775 | 5 | 9 |
| 2,000 sq ft | 2 | 2,105 | 6 | 11 |
| 2,500 sq ft | 2 | 2,435 | 7 | 13 |
| 3,000 sq ft | 2 | 2,600 | 7 | 13 |
Square metres and litres
Keep one unit system through the division. The two-storey 2,000 sq ft net wall is 2,105 × 0.09290304 = 195.5608992 m², shown to 7 decimal places. Gross wall area is 2,340 × 0.09290304 = 217.3931136 m² on the same rounding, and the 235 ft² of openings are 235 × 0.09290304 = 21.8322144 m². One US gallon is 3.785411784 litres. The unrounded 16.84 gallons are 16.84 × 3.785411784 = 63.74633444256 litres. The 17-gallon purchase is 17 × 3.785411784 = 64.352000328 litres.
Coverage of 250 ft² per US gallon is 250 × 0.09290304 ÷ 3.785411784 = 6.13559668677779 m² per litre. Divide the square metres by that figure. Dividing square metres by 250 counts a different quantity. The calculator keeps coverage labelled as square feet per US gallon even when the wall dimensions are metric.
Do it in order
- Use a measured perimeter, or one of the example rectangles only when you are checking this table.
- Multiply by the wall height to the eave: 9 ft for the one-storey rows, 18 ft for the two-storey rows. Add each gable separately as base × vertical height ÷ 2.
- Subtract two 20 ft² doors and one 15 ft² window per 10 ft of perimeter, or the openings you actually measured.
- Multiply by the coats you will apply and divide by the coverage on the can. Round up to whole gallons. Set the calculator waste field to 0 to match these rows.
Planning boundary
These gallons follow the stated rectangles, eave heights, opening sizes and labelled coverage. They leave out gables, trim, soffits, spraying loss and a separate primer. They do not specify surface preparation, lead-safe work, moisture limits or an installed price.
Sources checked
Each link supports the point named in the text. A citation is not a product endorsement or a price for your site.
- Behr — How much exterior paint do I need? Perimeter × height, 15 ft² window, 20 ft² door, 250–400 ft² per gallon, and more paint on porous or rough surfaces (opened 27 October 2026)
- Behr Premium Plus Exterior Flat No. 4050 technical data sheet — 250 sq ft/gal at 6.4 mils wet and 400 sq ft/gal at 4.0 mils wet; coverage depends on application method and substrate porosity; spray loss excluded (sheet marked 10/25, opened 27 October 2026)
- Sherwin-Williams Duration Exterior Acrylic Flat K32 — 250–300 sq ft per gallon; one coat on repaint and two coats on bare surfaces (data sheet marked 3/2026, opened 27 October 2026)
- Benjamin Moore Regal Select Exterior Flat 261 — spread rate 300–400 sq ft per gallon depending on surface texture and porosity (sheet 261 US 091426, opened 27 October 2026)
How many gallons of paint for the exterior of a 2000 sq ft house?
At 250 sq ft per gallon and the rectangles on this page, a 2,000 sq ft house needs 11 US gallons for two coats on one storey, or 17 US gallons on two storeys. The one-storey net wall is 1,310 ft² and 1,310 × 2 ÷ 250 = 10.48. The two-storey net wall is 2,105 ft² and 2,105 × 2 ÷ 250 = 16.84. At 400 sq ft per gallon those two-coat purchases are 7 and 11 gallons.
How much exterior paint for a 1500 sq ft house?
A 1,500 sq ft house needs 10 US gallons for two coats on one storey, or 15 US gallons on two storeys, at 250 sq ft per gallon. The net walls are 1,160 ft² and 1,775 ft². At 400 sq ft per gallon the two-coat purchases are 6 and 9 gallons. One coat is the other column in the same row.
How many gallons of exterior paint for a 2500 sq ft house?
A 2,500 sq ft house needs 12 US gallons for two coats on one storey, or 20 US gallons on two storeys, at 250 sq ft per gallon. The net walls are 1,460 ft² and 2,435 ft². At 400 sq ft per gallon the two-coat purchases are 8 and 13 gallons.
Is the square footage of a house the same as the exterior wall area?
No. Floor area is the plan of the living space. Wall area is the perimeter times the height to the eave, after doors and windows. On this page a 2,000 sq ft one-storey house has 1,310 ft² of net wall, and a 2,000 sq ft two-storey house has 2,105 ft².
Does stucco, brick or bare wood need more exterior paint?
Behr’s how-to, opened 27 October 2026, says a porous, rough, textured or previously unpainted surface will generally require more paint. The No. 4050 data sheet ties that to porosity: 250 sq ft per gallon at the thicker film and 400 at the thinner film. Duration’s sheet lists stucco, masonry and wood at 250–300 sq ft per gallon, and it calls for two coats on bare surfaces. Use the low end of the can you are buying. This page does not add a second, unsourced percentage for stucco.