Paint calculator
Work out how much paint to buy. Measure walls, subtract openings, add coats and use the coverage printed on your paint tin.
Rectangular room mode or a direct total area; up to 20 coats and 100% extra allowance. Openings cannot exceed wall area. Whole containers are limited to 1 billion. Unit changes preserve the entered numbers. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Paint calculator
- Enter room dimensions or a total surface area, then subtract measured openings.
- Set coats, coverage, allowance and container size from your chosen product.
- Review whole containers and download the estimate.
Useful next steps
Measure the surfaces you will paint
For a rectangular room, enter length, width and wall height. The calculator adds the four walls and can include a flat ceiling. Enter the combined area of doors, windows and other unpainted wall surfaces to subtract. For several rooms, irregular walls or a measured surface total, choose Direct area instead.
Use your paint's coverage per coat
The paint amount is the net area multiplied by the number of coats, divided by coverage. Coverage varies with the product and surface. Use the label on your chosen paint, then enter an extra allowance for your project. US gallons and imperial gallons are separate choices because they hold different volumes.
Round up to containers you can buy
Enter the amount in one container. The result shows calculated paint volume, whole containers and the surplus created by rounding. A 4 × 3 metre room with 2.5 metre walls, 3 square metres of openings, two coats and 10 m²/L coverage needs 6.4 litres before allowance. Adding 10% gives 7.04 litres, or two 5-litre containers.
Keep the estimate
Download the values as CSV and save a text or JSON report with formulas and assumptions. Processing stays in your browser. The estimate does not measure surface condition or guarantee a manufacturer's coverage.