Paint calculator: how much paint do I need?
Measure the rooms, take off the doors and windows, and see the litres and the tins to buy for walls, ceilings, trims and primer, for one room or the whole job.
Work out the paint
No sign-up. Add the rooms, and the litres and tins add up as you go. Nothing is uploaded.
Open the paint calculatorOpens in a new tab. Works on a phone, tablet or computer.
What it does
- Room by room: length, width and height for each room, or a single wall for a feature wall or an outside wall.
- Less doors and windows: takes off each door and window, plus anything else you won’t paint.
- Walls, ceilings and trims: each with its own coats and spread rate, a primer or sealer coat where you need one, and wall colours kept apart.
- Real tin sizes: rounded up to 1, 2, 4, 10 and 15 L tins, picking the cheapest mix, with extra for waste and touch-ups.
- Ready for the quote: copy the paint list into a quote, an order or a message, or print it.
How much paint for a room
| Room | Wall area | Paint for 2 coats | Tins |
|---|---|---|---|
| 3 × 3 m | 25.3 m² | 3.5 L | 4 L |
| 4 × 3 m | 30.1 m² | 4.1 L | 4 L + 1 L |
| 4 × 4 m | 34.9 m² | 4.8 L | 4 L + 1 L |
| 5 × 4 m | 39.7 m² | 5.5 L | 4 L + 2 L |
| 6 × 5 m | 49.3 m² | 6.8 L | 2 × 4 L |
Walls only, 2.4 m high, one door and one window, at 16 m² a litre with 10% extra. Ceilings, trims and primer are on top.
How to use it
- Add each room with its length, width and height, and count the doors and windows.
- Tick what you’re painting in each room: walls, ceiling, and doors and trims.
- Set the coats and spread rate from the tin, and tick primer for new or bare surfaces.
- Copy or print the paint list for the order and the quote.
Common questions
How much paint do I need for a bedroom?
A 4 × 3 m bedroom with a 2.4 m ceiling, one door and one window has about 30 m² of wall. Two coats at 16 m² a litre is about 3.8 L, or 4.1 L with 10% extra: a 4 L tin and a 1 L tin. The ceiling (12 m²) needs about 1.7 L, so a 2 L tin.
How many square metres does a litre of paint cover?
Most interior wall and ceiling paints cover roughly 12 to 16 m² a litre for each coat on a smooth, sealed surface. Primers, sealers and textured or exterior coatings often cover less. The spread rate is printed on the tin and the product’s data sheet, so use that figure.
How many coats of paint do I need?
Two coats for most repaints. A big colour change, a deep colour or a patchy old finish may need a third. New plaster, bare timber and patched areas need a primer or sealer first, which you can tick for walls, ceilings or trims.
Do I take off doors and windows?
Yes. The calculator takes off a standard 820 × 2040 mm door and a 1500 × 1200 mm window for each one you count, and you can change both sizes. Use “Take off” for anything else that isn’t painted, such as built-in robes or a tiled splashback.
Why does it pick a 4 L and a 1 L tin instead of a 10 L?
It picks the tins that cost the least at typical trade prices. Bigger tins are cheaper a litre, so it moves up to a 10 L or 15 L once that works out cheaper than a few small tins. Untick any size the product doesn’t come in.
Is anything uploaded?
No. It all runs in your browser, works offline once open, and remembers your rooms and settings on your device.
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