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Wallpaper rolls counted properly, by drops.
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Paint Calculator
Litres and tins for a room, doors and windows deducted.
Paint Calculator tool
Each taken as 1.8 m².
Each taken as 1.5 m².
From the tin. Usually 10 to 14 for emulsion.
Optional.
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Paint needed
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Tins to buy
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Area to paint
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Per coat
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Cost
| Measure | Value |
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Coverage on the tin assumes a smooth, previously painted surface. Bare plaster, textured walls and a strong colour change all take substantially more, and a first coat on new plaster can take half again.
About the Paint Calculator
Paint Calculator works out the litres and tins a room needs, with the doors and windows taken out and the number of coats applied. It uses 1.8 square metres for a door and 1.5 for a window, which are typical, and the deduction matters: on a small room the openings can be a tenth of the wall area.
Coats are where estimates usually go wrong. Two coats is standard for a repaint in a similar colour, and the paint needed doubles accordingly. Covering a dark colour with a light one often takes three, and new plaster needs a mist coat first -- diluted paint that soaks in -- which is not counted here because it uses watered-down paint.
Coverage figures on a tin assume a smooth, sealed, previously painted surface. Textured walls, bare plaster and woodchip all take more, sometimes half again. If the surface is not ideal, reduce the coverage figure rather than trusting the tin, and the result will be closer.
The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.
Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.
How to use the Paint Calculator
- Choose measurements inThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
- Enter room length, room width and wall heightDecimals are fine, and thousands separators are accepted and ignored.
- Read the paint needed, tins to buy and area to paintThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows paint needed, tins to buy, area to paint, per coat and cost together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The paint calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Working out paint for a room before buying
- Including the ceiling in the estimate
- Comparing two coats against three for a colour change
- Costing a decorating job by tins
Frequently asked questions
How many coats do I need?
Two for a repaint in a similar colour. Three when covering a much darker colour, and new plaster needs a diluted mist coat first.
Should I deduct doors and windows?
Yes for anything significant. The calculator uses 1.8 m² per door and 1.5 m² per window, which you can scale by entering fractional counts.
Why does my paint not cover as far as the tin says?
Coverage figures assume a smooth, sealed surface. Texture, absorbency and a strong colour change all reduce it, sometimes by a third.
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.