Estimate how much paint you’ll need for a room, a wall, or a ceiling. Enter your measurements, choose coats, and we’ll do the math.
Your estimate will appear here.
Enter your room dimensions to get started.
Your estimate
L
of paint
What to buy
- Walls
- Ceiling
- Extra allowance
How we calculated this
- Wall area
- Ceiling area
- Doors/windows deducted
- Paint coverage
- Coats
- Estimated paint
Calculated in your browser. Nothing is uploaded.
How the estimate is worked out
You need enough paint to cover the area you will actually paint, for each coat, at the coverage printed on the can. That is all the calculator is doing: area × coats ÷ coverage, then a little extra if you asked for it.
How to calculate paint for a room
For a rectangular room, wall area is 2 × (length + width) × height. Ceiling area is length × width. Decide whether you are painting walls, the ceiling, or both. Subtract openings if they are large enough to matter, then apply coats and coverage.
How much area does a litre of paint cover?
There is no universal figure. Coverage depends on the product, how you apply it, and how absorbent the surface is. Many interior paints claim something in the region of 8–12 m² per litre (or a few hundred square feet per gallon). Use the number on your tin. The default in this tool is only a typical starting point, labelled as an estimate.
Should I subtract doors and windows?
Yes, if you have several large openings and you want a tighter buy. For one standard door in a modest room, the difference is often small. Detailed estimate lets you add door and window counts, and the real sizes, so the result can be tighter. Quick estimate skips openings on purpose so you can get a number in seconds.
How many coats of paint do I need?
Two coats is a common starting point, not a law. A small colour change on a sealed wall may need less. Going from dark to light, painting new plaster, or using a thin paint may need more. Primer, if you use it, is an extra pass over the same area.
How much extra paint should I buy?
A modest allowance — often around 10% — covers touch-ups and the fact that walls are not a laboratory test card. It does not make the result exact. If you might need to match the batch later, keeping a little leftover is usually wiser than running out mid-wall.
Paint calculator formula
- Wall: width × height
- Room walls: 2 × (length + width) × height
- Ceiling: length × width
- Paint volume: paintable area × coats ÷ coverage
- Final estimate: paint volume + extra allowance
The recommended can mix is a practical purchase suggestion, not a second calculation of coverage.
How to use it
Choose the surface
Start with room, wall, or ceiling so you only see the measurements that matter.
Enter the size
Use metres or feet. Quick estimate keeps this short; Detailed estimate adds coverage, openings, and extra paint.
Set coats
Two coats is a common starting point. Change it if the surface or colour change needs more or less.
Read the estimate
You’ll get a calculated amount and a practical purchase suggestion. It is an estimate, not a guarantee.
Questions
How do I calculate how much paint I need?
Work out the paintable area, multiply by the number of coats, then divide by the coverage printed on the can. This calculator does that for a room, a wall, or a ceiling.
How much paint do I need for a room?
For the walls of a rectangular room, area is 2 × (length + width) × height. Subtract doors and windows if you want a tighter number, then apply coats and coverage.
How many square metres does a litre of paint cover?
It depends on the product and the surface. Many interior paints sit around 8–12 m² per litre, but you should use the figure on your can. There is no single number that fits every paint.
Should I subtract windows and doors from the wall area?
If you have several large openings, yes — it avoids buying paint you will not put on the wall. For a small room with one door, the difference is often modest. Quick estimate skips openings so you can get a number quickly. Detailed estimate lets you add door and window counts and sizes.
Can I use this calculator for a ceiling?
Yes. Choose Ceiling if you are only painting the ceiling, or choose Room and then Walls + ceiling if you want both. Ceiling area is length × width.
Can I use metric or imperial measurements?
Yes. Switch Units next to Room size. Metric uses metres and litres; imperial uses feet and gallons. Coverage figures update to match.
How many coats of paint should I use?
Two coats is a common starting point, not a rule. A similar colour on a sound wall may need less. A dark-to-light change, a thirsty surface, or a thin paint may need more.
How much extra paint should I buy?
A small extra amount — often around 10% — helps with touch-ups and real-world variation. Coverage on the wall is rarely identical to the lab figure on the tin.
What if my room has different wall heights?
This calculator assumes a rectangular space with one height. For a split-level or sloped wall, estimate each wall separately in Wall mode and add the amounts.
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