Coverage varies by paint, surface and application. Add doors/windows separately if you need a more precise estimate.
How to estimate paint required
- Measure the total length of the walls and the wall height.
- Enter the number of wall sections or walls represented by your measurement.
- Use the coverage figure printed on the paint container, not a generic value if the manufacturer provides one.
- Enter the number of coats and compare the estimated litres with available can sizes.
Worked example
If the total wall length is 20 ft, wall height is 9 ft, coverage is 100 sq ft per litre and you need 2 coats, the wall area is 20 × 9 = 180 sq ft. The estimated paint volume is 180 × 2 ÷ 100 = 3.6 litres before any separate allowance for surface absorption or touch-ups.
What affects the estimate?
Rough or porous plaster, dark-to-light colour changes, primer, application method and the actual product can change coverage. This simple calculator estimates rectangular wall area and does not automatically subtract doors or windows. Measure those separately if precision matters, and follow the paint manufacturer's preparation and coverage instructions.
Worked example: estimating paint for a room
Assume four walls are each 12 ft long and 9 ft high. Before subtracting doors or windows, the gross wall area is 12 × 9 × 4 = 432 sq ft. If the paint label states coverage of 100 sq ft per litre per coat and you plan two coats, the estimate is 432 × 2 ÷ 100 = 8.64 litres. The calculator rounds the purchase estimate to a practical half-litre increment, but pack sizes and actual coverage may change what you buy.
How to get a better estimate
- Use coverage stated on the specific paint product label; do not assume every paint covers the same area.
- Measure each wall separately if the room is irregular or has sloped ceilings.
- Subtract large openings if you want a closer estimate, but account for reveals and small surfaces separately.
- Porous plaster, rough textures, colour changes and application method can increase consumption.
- Primer is a separate product and is not included unless you calculate it separately.
This calculator estimates liquid quantity from area, coats and the coverage figure you enter. It does not predict the finish, choose a paint system or replace the manufacturer's instructions. For large or costly projects, confirm quantities with your painter or supplier.
For flooring measurements, see the Square Feet & Area Guide and Tile Calculator.