Paint Calculator
Measure the surfaces that will actually be coated, subtract eligible openings, and apply the selected number of coats. Product-specific coverage remains editable because texture, color change, and application method affect yield.
How to use the Paint Calculator
Enter room dimensions and ceiling choice or a known area, plus openings, coats, label coverage, and extra-material percentage.
Review manufacturer coverage, primer needs, surface porosity, texture, color transition, overspray, and whether trim is measured separately.
Read net surface area, required US gallons, and the number of whole one-gallon cans.
Formula
Room wall area = 2(length + width) × height; optional ceiling = length × width. Net area = measured area − openings; gallons = net area × coats × (1 + extra rate) ÷ label coverage.
Example
A 400 ft² net wall area with 2 coats and 350 ft² per gallon requires 800 ÷ 350 = 2.286 gallons before waste and container rounding.
Assumptions and limitations
- Surfaces are represented by measured flat areas and the entered coverage rate already reflects the chosen paint and application conditions.
- Paint Calculator treats the entered values as estimates and does not infer missing project, account, or personal details.
- Calculations retain working precision except where the cited method requires an intermediate rounding step; displayed values are then formatted separately. Source rules and dated rates must be rechecked when they change.
Sources
- U.S. Environmental Protection Agency: Renovation, Repair and Painting ProgramSafe painting and renovation context for pre-1978 buildings. Reviewed 2026-08-14.
- National Institute of Standards and Technology: SI Units — LengthLength, area, volume, and unit-conversion conventions. Reviewed 2026-08-14.
- National Institute of Standards and Technology: Circumference, Area and VolumeOfficial formula, rate, or program guidance used by this calculator. Reviewed 2026-08-14.
Related construction calculators
Frequently asked questions
How does the Paint Calculator work?
Room wall area = 2(length + width) × height; optional ceiling = length × width. Net area = measured area − openings; gallons = net area × coats × (1 + extra rate) ÷ label coverage.
What information should I enter in the Paint Calculator?
Enter room dimensions and ceiling choice or a known area, plus openings, coats, label coverage, and extra-material percentage, then verify manufacturer coverage, primer needs, surface porosity, texture, color transition, overspray, and whether trim is measured separately.
What should I verify before using this Paint Calculator result?
Surfaces are represented by measured flat areas and the entered coverage rate already reflects the chosen paint and application conditions.
Reviewed 2026-08-14 · room-or-area-v2 · content-2026-08-14 · Trusty Calculator Editorial Team