Paint calculator – how much paint you need
Enter the room size, subtract windows and doors, choose the number of coats and the coverage from the label. You get litres, number of cans, primer and an estimated cost.
1. Room
2. Windows and doors (subtracted)
3. Paint
Result
Shopping list
How we calculate
Wall area = 2 × (length + width) × height minus windows and doors; ceiling = length × width. Litres = area × coats ÷ coverage (m²/l), plus allowance. Cans are rounded up to whole packs. Primer: one coat over the whole area.
The result is an estimate – actual usage depends on substrate absorbency, colour change (dark over light = more coats) and tools (a roller uses less than a brush).
How the calculator works – questions and answers
How much paint for a 20 m² room?
A 4 × 5 m room with a 2.6 m ceiling has about 47 m² of walls; after subtracting a door and two windows about 42 m² remain. With two coats at 10 m²/l you need about 8.5 l for the walls plus about 4 l for the ceiling – with a 10 % allowance that is 4 + 2 cans of 2.5 l.
What is paint coverage and where do I find it?
Coverage is the number of m² one litre covers in one coat – printed on the label (e.g. "up to 12 m²/l"). On absorbent new plaster take a value 20 % lower; on a primed, smooth wall use the upper value.
How many coats of paint are needed?
Two as standard. One is enough when refreshing with the same colour; three when covering a dark colour with a light one, for intense colours (red, yellow) or on new plaster without primer.
Do walls need primer before painting?
Yes on new plaster, gypsum skim, plasterboard and after filling – primer evens out absorbency, cuts paint usage by up to 20–30 % and prevents streaks. On a previously painted, clean wall the paint alone is usually enough.
How much does painting a room cost with labour?
The calculator counts materials. A painter in Poland in 2026 charges roughly 15–30 PLN/m² for two coats (more with priming and filling). A 4 × 5 m room has about 60 m² of walls and ceiling, i.e. 900–1800 PLN labour plus 300–700 PLN paint. Use our renovation planner for a full estimate.
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