Paint Calculator
Last updated: July 2026
Estimate paint gallons from wall area and coverage.
Estimated paint to buy
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- Coverage required: —
- Exact estimate: —
On this page
Quick summary: Estimate paint gallons from wall area and coverage. Enter the requested values, calculate, review the result, and compare more than one realistic scenario before making a decision.
Read the complete guide
What this calculator does
The Paint Calculator estimates how much paint is needed for a wall or room based on surface area and expected coverage. It helps with budgeting and deciding how many cans to buy before starting a decorating project.
How to use the calculator step by step
Enter the wall dimensions or total paintable area, then provide the paint coverage rate and number of coats if the calculator asks for them. Exclude large doors and windows only when their combined area is significant.
How the calculation works
Paint required is based on total paintable area multiplied by the number of coats, then divided by the coverage provided by one unit of paint. For example, 400 square feet with two coats and coverage of 350 square feet per gallon requires about 2.29 gallons.
Worked example and scenario testing
A room has 520 square feet of paintable wall area. With two coats, the effective area is 1,040 square feet. If one gallon covers 350 square feet, the estimate is about 2.97 gallons, so buying 3 gallons would be the theoretical minimum.
How to interpret your result
The estimate is a planning quantity, not a guarantee. Rough surfaces, strong color changes, porous materials, and application technique can increase actual paint use.
Accuracy, assumptions, and limitations
Coverage printed on the paint container is usually based on controlled conditions. Primer, texture, overspray, waste, touch-ups, and leftover paint are not always included.
Common mistakes to avoid
Common errors include forgetting the second coat, confusing floor area with wall area, or assuming every paint product has the same coverage rate.
Privacy and browser-based calculations
The calculator only uses room dimensions and paint assumptions. No personal data is required.