Interior paint guide
Paint calculator: how much paint do I need?
Measure the room, subtract doors and windows, account for every coat, then divide the paintable area by the coverage printed on the paint can.
Enter your dimensions in the free calculator for an instant estimate in gallons and one-gallon cans.
Use the paint calculatorHow the paint estimate works
For a rectangular room, wall area is the room perimeter multiplied by wall height. ProjectReady deducts about 21 square feet for each standard door and 15 square feet for each window, multiplies the remaining area by the number of coats, and divides by your paint's coverage rate.
Gallons = ((2 × (length + width) × height − openings) × coats) ÷ coverage per gallon
Measurements to collect
- Room length, width, and wall height in feet
- Number of doors and windows
- Number of planned coats
- Coverage per gallon shown by the manufacturer
Before you buy
Coverage varies with surface texture, color change, application method, and product. Porous or repaired walls may need primer and more paint. Use this result as a shopping estimate and confirm the final quantity against the product label.