Paint Calculator
Estimate paint from your measured surface area and entered product coverage. Subtract unpainted openings, set the coat count, and enter the container size. Coverage is for one coat and uses the selected area and volume units. The required coverage field starts empty; check your paint label and surface conditions. No waste allowance is added. Surface geometry uses the shared area calculator, rounded to 15 significant digits before the container calculation; entered area and coverage fractions retain exact ratios.
Calculation result
Net area = total surface area − openings; paint = net area × coats ÷ entered coverage; containers = ceiling(paint ÷ container volume).
Primary source: Behr manufacturer guidance on surface area, openings and per-coat coverage. NIST SP 811 conversion factors supplies the unit definitions.
Worked example: 800 ft² − 100 ft² of openings = 700 ft². Two coats at an entered 350 ft²/US gallon need 700 × 2 ÷ 350 = 4 US gallons, or four 1-gallon containers. A 100 m² surface, zero openings and one coat at 10 m²/L needs 10 L, or four 3-L containers.
How to use this tool
Enter total paintable surface area or switch to rectangle dimensions and add surfaces. Set openings in the same squared unit. Enter the label coverage for one coat, coats and container volume; changing units changes the interpretation of entered numbers, so update them to match.
Frequently asked questions
Where does the coverage value come from?
You enter it from the product label or your own measured coverage. Texture, porosity and application can change the paint required. No brand coverage value is assumed.
How are containers rounded?
Divide the calculated paint volume by the entered container volume and round upward to a whole container. The result includes no extra allowance for waste or future touch-ups.
Is this calculator free and private?
Yes. Arithmetic runs on your device. Your entries are not uploaded or saved to browser storage, and no sign-up is needed.