A 4 × 4 m bedroom
16 m of wall × 2.5 m = 40 m², minus one door and two windows = 35.1 m². Two coats at 10 m²/L need 7.02 litres.
Paint Calculator
Estimate how much paint a room needs from the wall size, doors, windows and number of coats.
Result
Enter your values and select Calculate to see the result.
Result
Enter your values and select Calculate to see the result.
Runs in your browser — nothing you enter is sent to a server.
How the Paint Calculator works
Enter the total length of the walls (add up each wall) and their height. The calculator takes away about 1.9 m² (20 ft²) for each door and 1.5 m² (16 ft²) for each window, multiplies by the number of coats and divides by the paint's coverage — about 10 m² per litre, or 400 ft² per US gallon, on smooth walls. Change the coverage to match your tin.
Formula
paint = (wall length × height − doors − windows) × coats ÷ coverage
Examples
Ceilings
Use the room's length × width as the area: enter the width as the wall length and the length as the height.
Frequently asked questions
Do I need primer?
Yes for new plaster, bare wood, stains or big colour changes. Primer covers differently, so calculate it separately.
Why does textured paint need more?
Rough and porous surfaces soak up paint; coverage can drop by a third or more.
How much extra should I buy?
Round up to whole tins and keep some for touch-ups — colours can vary slightly between batches.
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