Two-bedroom flat (metric)
Input Walls 120 m², ceiling 30 m², 2 doors, 3 windows, 2 coats, coverage 12 m²/L, 2.5 L cans.
Result About 24.8 L needed → 10 cans of 2.5 L (≈ 6.6 gal).
Paint Coverage Calculator
Home & RenovationEstimate litres or gallons of paint from wall area, ceilings, openings, coats and the coverage printed on the tin.
Your inputs
Result
Paint needed
—
L
- Cans to buy — cans
- Equivalent amount — gal
- Area with coats — m²
- Net wall + ceiling area — m²
- Deducted openings — m²
Change any input and the result updates instantly.
Formula and rules
- Deducted area = doors × 1.8 m² + windows × 1.5 m² (or 20 ft² and 15 ft² in imperial)
- Net area = wall area + ceiling area − deducted area
- Total painted area = net area × number of coats
- Paint needed = total painted area ÷ coverage × (1 + extra allowance)
- Cans = round up (paint needed ÷ can size)
Worked examples
Open-plan room (imperial)
Input Walls 1,200 ft², ceiling 300 ft², 3 doors, 4 windows, 2 coats, coverage 350 ft²/gal, 1 gal cans.
Result About 8.3 gal needed → 9 one-gallon cans (≈ 31.4 L).
FAQ
Should I deduct doors and windows from the wall area?
Yes, but the calculator already does it with average sizes (1.8 m² per door, 1.5 m² per window). If your openings are unusually large, measure them and adjust the wall area instead.
Why does the tin say 12 m² per litre but I need more?
Coverage figures assume a smooth, sealed surface and a single coat. Bare plaster, render or a strong colour change absorb more paint, which is what the extra allowance covers.
Can I use the same calculation for primer or ceiling paint?
Yes, but enter the coverage printed on that product and keep one coat for primer. Primer usually covers less than topcoat on porous surfaces.
Disclaimer: Results follow the formula shown on this page and are for reference only. Real-world quantities vary with materials, technique and conditions, so allow a margin before ordering.