Paint coverage calculator

Work out how many litres of paint to buy for a wall, ceiling or room, based on the area, number of coats and your paint's stated coverage.

Area to paint (m²)Number of coatsCoverage per litre (check your paint tin) (m²/L)

Result

Paint required

How to use this calculator

Measure the total area you're painting.
Check the coverage figure on your paint tin (it varies by brand and surface) and enter it, or keep the default estimate.
Enter how many coats you're applying.
Read the litres required.

Assumptions

The default 12m²/L is a typical mid-range emulsion figure — real coverage ranges roughly 10–14m²/L and is lower on bare plaster or textured surfaces.
No allowance is added for spillage or a second colour test patch.

Technical details: what the fields mean

Area to paint areaM2: Total surface area to paint, in square metres.
Number of coats coats: How many coats you're applying — 2 is standard for most emulsions.
Coverage per litre (check your paint tin) coveragePerLitreM2: How many square metres one litre covers per coat. This varies significantly by paint brand and surface porosity — always check the tin.

Methodology

Litres = (area × coats) ÷ coverage per litre.

Worked example

20m² wall, 2 coats, 12m²/L coverage

Inputs: areaM2=20, coats=2, coveragePerLitreM2=12

Result: 3.3 litres required

Practical guidance

Round up to the next full tin size — leftover paint is useful for touch-ups.
Bare plaster and new woodwork often need a mist coat / primer first, which uses more paint than the topcoats.

Common mistakes

Using the default coverage figure instead of the one printed on your actual tin.
Forgetting that a mist coat on new plaster covers less area per litre than a standard coat.

FAQs

How much paint do I need for a 20m² wall?

With 2 coats at 12m²/L coverage, about 3.3 litres — but check your specific paint's coverage first.

Why does my paint tin's coverage figure matter so much?

Coverage varies by 30% or more between paint brands and finishes (matt vs. silk, trade vs. retail), so using the tin's own figure gives a far more accurate result than a generic default.