How do I calculate exterior paint for house siding and gables?
Gallons = ((sum of wall and gable areas − openings + trim areas) × coats) ÷ coverage, with the selected waste allowance.
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Exterior paint calculator
Estimate exterior paint for walls, openings, and gables with coats and waste included.
- Metric and imperial units
- Instant updates as inputs change
- Data is calculated in this browser only
Results are planning estimates. Confirm site dimensions, product specifications, and installation waste before purchasing.
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Calculation notes
Understand the Exterior paint calculator
Each wall run is length × height. Window, door, and garage-door openings are deducted, then gables or trim are added. Net area is multiplied by coat count and divided by coverage.
How many gallons cover a 40 by 30 ft house with two coats?
A 40 × 30 ft rectangular house with 10 ft walls has 1,400 sq ft of wall area. Less 200 sq ft of openings, two coats at 350 sq ft/gal require about 7 gallons before waste.
Should trim, doors, and siding be calculated separately?
- Separate wall paint from trim and door products when colors or finishes differ.
- Measure each elevation instead of relying only on floor area.
What jobsite conditions increase exterior paint usage?
- Defaults reflect common U.S. exterior-paint coverage rates.
- Brick, rough stucco, and unprimed surfaces commonly require more paint.
- Siding texture, access, overspray, primer, and weather conditions affect real consumption.
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