Paint Calculator
Estimate gallons of wall paint and whole one-gallon cans.
Estimate wall paint
Use the paint manufacturer's coverage figure when available.
Estimated paint
Gallons required
- Whole one-gallon cans
- 2
- Paintable wall area
- 334 sq ft
- Area across all coats
- 668 sq ft
Planning estimate only. Surface and application conditions affect actual coverage.
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Estimate paint for interior walls
Measure the total distance around the room and the wall height. Enter the number of standard doors and windows, the planned coats, and the coverage listed by the paint manufacturer.
The estimate subtracts 20 square feet for each door and 15 square feet for each window. Unusually large openings should be handled by adjusting the entered perimeter or treating the result as a rough estimate.
Formula
Gross wall area equals perimeter multiplied by height. Paintable area equals gross wall area minus estimated opening area. Gallons equal paintable area multiplied by coats, divided by coverage per gallon.
The whole-can figure rounds up to one-gallon containers. Stores may offer other sizes, so compare the unrounded gallon requirement with the available container mix.
Before buying paint
Confirm measurements and product coverage. New drywall, repairs, highly textured surfaces, sprayers, and dramatic color changes can alter actual consumption. Primer is a separate product and is not included.
Frequently asked questions
How does the calculator estimate wall area?
It multiplies the room perimeter by wall height, then subtracts 20 square feet per door and 15 square feet per window. The remaining area is multiplied by the number of coats.
Should I use the coverage number on the paint can?
Yes. Coverage varies by product, surface texture, application method, and color change. The manufacturer's figure is a better starting point than a generic value.
Does the estimate include ceilings or trim?
No. This calculator estimates walls only. Calculate ceilings, doors, baseboards, and other trim separately using the coating intended for each surface.
Why might I need more paint than the estimate?
Porous or textured walls, major color changes, spills, touch-ups, and application losses can increase usage. Keep the estimate as a planning figure and consider project-specific extra material.