Paint Calculator
Less guessing. More painting.
Find out how much paint your project needs. Enter your wall measurements, subtract doors and windows, and get an instant estimate.
🖌️ Enter your measurements
💡 For walls of different sizes, calculate each group separately and add the paint quantities. This tool assumes all entered walls have the same dimensions.
🚪 Subtract openings
Assumes approximately 21 sq ft per door and 15 sq ft per window. Adjust the estimate if your openings differ.
🪣 Paint details
Check the coverage printed on your paint can. One US gallon equals approximately 3.785 litres.
📐 How to calculate how much paint you need
Start by multiplying the width and height of each wall to calculate its area. Add the areas together, then subtract doors and windows you won’t be painting.
Multiply the remaining area by the number of coats, divide by the paint’s stated coverage, and add a reasonable allowance for waste and touch-ups.
🧮 Example: Painting a room
Four walls measuring 12 feet wide by 8 feet high have a combined area of 384 sq ft. Subtracting one standard door and two windows leaves 333 sq ft.
For two coats, that’s 666 sq ft of coverage. At 400 sq ft per US gallon, plus 10% extra:
💡 Frequently Asked Questions
Two coats are common for interior walls, but the number depends on colour changes, surface condition, primer and the manufacturer’s instructions.
This calculator estimates walls only. Calculate the ceiling separately using its length and width, then add the required paint quantity.
No. Doors are subtracted as openings. Trim, baseboards and painted doors should be estimated separately.