Paint Quantity Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/3/2026
The amount of paint needed is found by multiplying the surface to paint by the number of coats, then dividing by the paint's coverage (shown on the can, in m²/L). Example: 20 m² with 2 coats and a coverage of 10 m²/L requires 4 L of paint.
Explanation
A paint's coverage (the number of m² covered per liter) is shown on the packaging and varies a lot depending on the type of paint (matte, satin, oil-based) and the surface's porosity: an already-painted wall absorbs less than freshly applied raw plaster, which may need an extra bonding primer coat. This calculator therefore doesn't set a universal default coverage — use the value shown on your paint can for a reliable result. Two coats are generally recommended for an even color, especially when making a big color change (for example repainting a dark wall white). To find the surface to paint from the room's dimensions, see our area calculator.
Example: 20 m² with 2 coats
Inputs
Surface: 20 m². Coverage: 10 m²/L. Number of coats: 2.
Calculation
First multiply the surface by the number of coats: 20 × 2 = 40 m² to cover in total. Then divide by the coverage: 40 ÷ 10 = 4 L.
Result
You need about 4 liters of paint for this project.
Frequently asked questions
Should I subtract the area of doors and windows?
For a precise calculation, yes: subtract the area of openings from the total wall area before entering it here. Many DIYers, however, keep a small safety margin rather than precisely deducting small openings, so as not to fall short in case of touch-ups.
Where do I find my paint's coverage?
It's shown on the can's label, usually expressed in m²/L or in total m² for the whole can. If it's not indicated, 10 to 12 m²/L per coat is a common value for a standard wall paint on an already-painted surface.
Does a primer coat count as a coat?
No, a bonding primer (useful on a raw, porous surface, or for a strong color contrast) has a different coverage than the finish paint and is added to the calculation separately: run a separate calculation for the primer using its own coverage value.