How much paint do I need
Litres of paint based on surface area, coats and product coverage.
Calculator inputs
Results
Enter your values and press “Calculate” to see the result.
In short
- What it calculates
- Litres of paint based on surface area, coats and product coverage.
- Formula used
Net area = area − openings- Example
- 45 m² of wall, 2 coats, coverage 10 m²/L and 3.6 m² of openings:
Paint calculator
Buying too little paint means a trip back to the shop and risking a slightly different batch; buying too much is money down the drain.
With the area, the number of coats and the coverage printed on the tin, the maths is straightforward.
How it works
Door and window openings are deducted, the net area is multiplied by the number of coats and divided by the product coverage.
Formula
Net area = area − openings
Litres = net area × coats ÷ coverage
Typical coverage: 10 to 12 m² per litre per coat
Worked example
45 m² of wall, 2 coats, coverage 10 m²/L and 3.6 m² of openings:
Net area: 41.4 m²
Litres: 41.4 × 2 ÷ 10 = 8.28 L
You need three four-litre tins.
Explanation
The coverage on the tin is optimistic
Manufacturers state square metres per litre under ideal conditions: a smooth, well-prepared surface, applied by roller, one coat over a similar colour. In practice a rough wall, textured render or a drastic colour change can halve the real coverage.
Two coats are almost always needed
A single coat leaves patchiness, especially in intense colours such as red or yellow, which cover worst. Over new unprimed walls, or going from dark to light, three may be needed. Primer costs less than an extra coat of coloured paint.
Preparation is half the job
Filling holes, sanding, removing dust and priming repaired areas determines the finish more than the quality of the paint. Expensive paint on a badly prepared wall gives a worse result than ordinary paint on a well-treated one.
Buy from one batch
Tins of the same colour can vary slightly in shade between production batches. If you will need several, buy them together and mix them with each other before starting to avoid visible differences on the wall.
Frequently asked questions
How many coats are needed?
Two as a rule. New plaster, a strong colour change or light paint over dark can require three.
Is coverage always the same?
No. It depends on how absorbent the wall is: a porous or unprimed surface can consume up to 30% more.
Why did my paint cover less than the tin says?
Because the stated coverage assumes ideal conditions. A rough, porous or unprimed surface absorbs considerably more paint.
Should I mix the tins before starting?
Yes, if you will use several of the same colour. Batches can vary slightly in shade, and mixing avoids visible differences.
Need to calculate something else?
These tools are often used alongside this calculator.