Exterior paint calculator
Estimate measured exterior walls. Add each wall or custom shape separately. Enter your measurements, adjust the assumptions, and leave with a shopping plan.
Buy with confidence.Transparent formulas. Your prices.
Saved on your device.
Measure siding, not house floor area
Add each elevation as its own wall. Use custom area for triangular gables: base × height ÷ 2. Subtract windows and doors once. Rough or porous surfaces require product-specific coverage; this tool does not infer it from building type.
Already know the net area? Use the paint coverage calculator to work from area or from paint you already have.
A worked example
A 30 ft wide elevation with 10 ft rectangular walls has 300 sq ft. Its triangular gable adds 30 × 6 ÷ 2 = 90 sq ft. Subtract a 3 × 7 ft door (21 sq ft) and two 3 × 4 ft windows (24 sq ft): 300 + 90 − 21 − 24 = 345 sq ft. Two coats at an entered 350 sq ft/US gal need 345 × 2 ÷ 350 = 1.9714 US gallons before extra; × 1.10 = 2.1686 gallons with 10% extra. With only 1- and 5-gallon containers enabled, the minimum-quantity purchase is three 1-gallon cans. Add the rectangle as an exterior wall and the 90 sq ft gable as custom area, using the same paint group.
Check before checkout
Coverage varies by product and surface. Use the label value, confirm coats and check the suggested container sizes are sold in your chosen finish. Do not combine different colours just to reduce rounding.
Questions worth answering before you paint
Does this include doors and trim?
Doors and windows are deducted as openings. To paint doors or trim, add a custom-area surface with its measured paintable area and a separate paint group. Include all faces you intend to paint.
Can I save without creating an account?
Yes. Save on this device stores one project locally. Download project keeps a portable file. Neither creates an online account.
Is this a guaranteed quote?
No. It estimates quantities and a budget from your inputs. Product performance, preparation and local prices can change the outcome.