Free calculator
Paint calculator
Enter the room or the wall area, the number of coats and the coverage printed on the can, and get how much paint to buy.
Result
- Wall area (gross)
- 45 m²
- Paintable area (net)
- 41.9 m²
- Paint needed (2 coats)
- 8.38 L
- Cans to buy (5 L)
- 2
- Total bought
- 10 L
Walls only. Add the ceiling area separately if you paint it, and a primer coat on new plaster.
How it works
Wall area of a room is the perimeter times the height: 2 × (length + width) × height. Doors and windows are deducted at typical sizes (about 1.9 m² or 20 sq ft per door, 1.2 m² or 13 sq ft per window). Paint needed = net area × coats ÷ coverage.
Coverage is the figure the manufacturer prints on the can, often around 10 to 12 m² per litre (350 to 400 sq ft per gallon) for emulsion on smooth, previously painted walls. Bare plaster, textured or dark walls absorb more, so use the lower end of the range or add a coat.
The calculator covers walls only. Add the ceiling area separately if you paint it, and count a primer or mist coat on new plaster as an extra coat.
Frequently asked questions
- How much paint do I need for a 12 x 12 ft room?
- With 8 ft walls that is 384 sq ft gross. Taking out one door and one window leaves about 350 sq ft; two coats at 400 sq ft per gallon is about 1.75 gallons, so two gallon cans.
- How many coats of paint do I need?
- Two coats is the usual assumption for a colour change on a painted wall. Covering a dark colour with a light one, or painting new plaster, often takes three including the primer.
- Is one litre of paint enough for one wall?
- At 10 m² per litre, one litre covers a 4 × 2.5 m wall once. Two coats need two litres, so a 2.5 L can is the practical minimum.
Guides
- How much paint do I need for a 12x12 room?
Gallons of paint for a 12 x 12 ft room with 8, 9 or 10 ft ceilings, one or two coats, a door and two windows deducted, plus the 4 x 4 m room in litres.