Paint Calculator
Enter the length, width and height of your room, the number of doors and windows and how many coats you plan. The paint calculator shows the paintable area and how much paint to buy, with a suggested can size and a margin for extra.
Runs in your browser. Your files are never uploaded.
Loading Paint Calculator…
How to use Paint Calculator
- Pick metres and litres, or feet and gallons.
- Enter the room length, width and height and the number of doors and windows. Edit their sizes if yours differ.
- Set the number of coats and the coverage printed on your paint tin. Tick Include the ceiling if you are painting it.
- Read the paintable area and the paint to buy, including the suggested cans.
How the estimate works
The calculator adds up the four walls, plus the ceiling if ticked, and subtracts the doors and windows. It multiplies the paintable area by the number of coats and divides by the coverage per litre or gallon.
- Walls = 2 x (length + width) x height.
- Ceiling = length x width.
- Paint = area x coats / coverage.
Choosing can sizes
The amount to buy adds about 10 percent. In metric it is then filled with 10, 5, 2.5 and 1 litre cans, with the last can rounded up. In imperial it uses 5 gallon and 1 gallon cans. Sizes in your local shop may differ, so treat the suggestion as a guide.
Buy a little extra
Buy 5 to 10 percent extra for touch-ups, spills and uneven surfaces. Keeping a little paint from the same batch also helps if you need to repair marks later.
Limits
All calculations happen in your browser, and nothing you type is uploaded or stored on a server. Results are estimates. They ignore skirting boards, trim, alcoves and sloped ceilings, and coverage depends on the surface and product. Dark colours, bare plaster and wallpaper removal can need more paint. Check your tin and ask the shop if unsure.
Why use this paint calculator tool
- Doors and windows removed. Door and window areas are subtracted from the walls, and their sizes are editable.
- Coats and coverage. Set the number of coats and the coverage per litre or gallon from your tin.
- Can size suggestion. Rounded up to 10, 5, 2.5 and 1 litre cans, or 5 and 1 gallon cans.
- Extra allowance. The amount to buy includes about 10 percent extra for touch-ups.
Frequently asked questions
How much paint do I need for a room?
Find the wall area, subtract doors and windows, multiply by the number of coats and divide by the coverage of your paint. For example, 40 square metres, two coats and 10 square metres per litre needs 8 litres. This calculator does the steps for you.
How do I measure a room for paint?
Measure the length, width and height of the room. The wall area is twice the length plus width, times the height. Count each door and window and enter their sizes so they are subtracted. Add the ceiling if you plan to paint it too.
What coverage should I use?
Use the figure printed on your paint tin, which varies by product. This tool starts at 10 square metres per litre or 350 square feet per gallon, which are common figures. Rough or porous walls take more paint, so use a lower number for them.
How many coats do I need?
Two coats is common for a good finish, and a new or very different colour may need more. A primer coat is separate. Change the coats field and the amount of paint updates straight away. You can change any value at any time and the result updates immediately, so it is easy to compare a few different options before deciding.
Is my room data uploaded?
No. Measurements are used only in your browser to calculate the result. Nothing is uploaded or saved on a server, and no account is needed. It works on your own device, so it is safe to use with private figures, and it keeps working if you go offline after the page has loaded.
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