Paint calculator
Enter the wall length, height, doors, windows and coats. You get the area to paint, the litres or gallons of paint and how many cans to buy.
Defaults to your region. Switch to compare any other scale.
Result
7 L
Paint needed
Exact amount: 6.93 L · 1.83 US gal · Cans to buy: 3 × 2.5 L
- Gross wall area36.4 m²
- Doors and windows (subtracted)− 4.9 m²
- Area to paint31.5 m²
- Total area incl. all coats63 m²
- Exact amount6.93 L
- Cans to buy3 × 2.5 L
- Other unit1.83 US gal
Tip
Check the coverage on your paint can: it depends on the product and the surface. Rough, porous or fresh plaster walls can need 20–30% more, and a strong colour change often needs a third coat.
About this tool
How much paint do I need?
Multiply the total wall length by the wall height, subtract doors (about 1.9 m² or 21 ft² each) and windows (about 1.5 m² or 15 ft² each), multiply by the number of coats and divide by the coverage on the can.
Typical coverage
Most interior emulsion covers 8–12 m² per litre (350–400 ft² per US gallon) per coat on smooth, primed walls. Porous or textured surfaces use more.
Worked example
A 4 × 3 m room has 14 m of wall. At 2.6 m high that is 36.4 m². Minus one door and two windows: 36.4 − 1.9 − 3 = 31.5 m². Two coats at 10 m²/L need 6.3 L; with 10% extra, about 6.9 L, so three 2.5 L cans.
Formula
Wall area = wall length × heightArea to paint = wall area − doors − windowsPaint = area × coats ÷ coverage × (1 + waste %)Cans = round up (paint ÷ can size)
How it is calculated
- Choose metric or US units.
- Enter the total length of the walls and their height.
- Enter how many doors and windows to leave out.
- Set the number of coats and the coverage printed on the can.
- Read how much paint and how many cans you need.
Questions
How much paint do I need for a 12 m² wall?
At a typical 10 m² per litre, one coat takes 1.2 L and two coats 2.4 L. A 2.5 L can is just enough; buy a little more for rough or porous walls.
Do I need two coats of paint?
Usually yes. Two coats give even colour and durability. A third coat helps when going from dark to light or painting fresh plaster without primer.
What size are doors and windows in this calculator?
A standard door counts as 1.9 m² (21 ft²) and a window as 1.5 m² (15 ft²). For large patio doors or windows, count them as two.