Paint Calculator
Calculate how much paint you need for a room. Enter room dimensions, number of coats, and paint coverage to get litres or gallons needed.
Check your paint tin — standard emulsion: 10–12 m²/litre
How to use
- Select metric (metres) or imperial (feet).
- Enter room length, width, and ceiling height.
- Enter number of doors and windows to subtract.
- Enter number of coats (usually 2).
- Enter paint coverage from your paint tin.
- Click Calculate.
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Estimating paint quantity correctly saves money and avoids multiple trips to the hardware store. The formula is straightforward: calculate the total paintable area (walls + ceiling, minus doors and windows), multiply by the number of coats, then divide by the paint's coverage rate (listed on the tin). Always add 10% for wastage, cutting-in, and touch-ups.
Coverage rates vary by paint type: standard emulsion covers 10–12 m² per litre on prepared surfaces; masonry paint covers 4–6 m²/litre; gloss covers 12–14 m²/litre. Rough or unpainted surfaces absorb more paint and reduce effective coverage. Always check the manufacturer's stated coverage on the tin.
Frequently Asked Questions
How many coats of paint do I need?
New or newly plastered walls typically need a mist coat (diluted emulsion) plus 2 full coats. Repainting with a similar colour: 1–2 coats. Painting a lighter colour over a dark one: likely 3 coats. White over red or yellow can take 4+ coats.
Why add 10% wastage?
Paint is wasted through brush/roller loading, drips, cutting-in edges, and touching up imperfections. 10% is a standard buffer. If the room has many angles, alcoves, or architectural features, add 15%.
Should I paint the ceiling the same as the walls?
Ceiling and wall paints are different products — ceiling paint is usually matt white with higher opacity for spray/roller application on a horizontal surface. This calculator includes the ceiling area separately so you can order the right quantities of each type.
How do I calculate paint for just the walls (no ceiling)?
Set the ceiling option to 0 by entering 0 for the coverage, or simply subtract the ceiling area (length × width) from the total result. Alternatively, note that the calculator shows wall area and ceiling area separately in the results.