Buy the right amount of paint the first time. Enter your wall area (or dimensions), the number of coats and the paint's coverage, and we'll tell you how much paint to buy — with an allowance for doors and windows so you don't over- or under-buy.
The walls
Paint needed
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Net area to paint—
Total area incl. coats—
Estimate only — porous, dark or textured surfaces use more. Calculations run in your browser.
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How to work out your wall area
Multiply each wall's height by its width and add them together for the total area, then deduct for doors and windows. If you'd rather not measure every wall, a quick estimate is the room's floor perimeter multiplied by the wall height. Enter that total here and set a deduction (around 10% is typical for a room with a door and a window or two) to avoid buying paint for surfaces you won't cover.
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Coats and coverage are everything
Paint tins state a coverage figure — often around 10–13 m² per litre for emulsion — but that's for one coat on a smooth, sealed, similar-coloured surface. Most jobs need two coats, which doubles the paint, and that's exactly what this calculator accounts for. Always check the specific product's stated coverage and number of recommended coats rather than assuming.
When you'll need more than the calculator says
Real surfaces are thirstier than the ideal. New plaster, bare wood and porous or textured walls soak up extra paint, and a dramatic colour change (especially light over dark, or vivid colours) can need an extra coat or a primer. Buy a little spare for touch-ups, and keep the batch number — matching paint later is difficult. The tool already suggests a ~10% buffer.
Frequently asked questions
How much paint do I need for a room?
Work out the total wall area (height × width of each wall, added up), deduct for doors and windows, multiply by the number of coats, then divide by the paint's coverage per litre. For a typical room that's often two to three litres per coat. This calculator does all of that for you and adds a buffer for touch-ups.
How many square metres does a litre of paint cover?
Most wall emulsions state around 10–13 m² per litre for a single coat on a smooth, sealed surface, but always check the specific tin. Porous, textured, bare or dark surfaces cover less, and you'll usually apply two coats. Enter the product's stated coverage in the calculator for the most accurate quantity.
Should I buy extra paint?
Yes — a little. Buying roughly 10% more than the bare calculation covers touch-ups, missed spots, thirstier patches and future repairs, and saves a frustrating second trip mid-job. Keep the leftover (and note the colour and batch number) for fixing scuffs later, since matching paint after the fact is notoriously hard. The calculator already suggests a safe buffer.
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