Measure rooms and openings, then estimate finish paint and primer cans using your coverage, coats and allowance.
Lengths accept decimals, fractions such as 1 1/2, and explicit units such as 12 in or 5' 6 1/2". Use a dot for decimals.
Room / surface 1
m
m
m
Doors and windows to subtract
m
m
Net paintable area 30 m².
Each coating below covers the full net area. Coverage values are examples. Enter the coverage from your own product label, per coat.
Coating 1
%
L
Finish paint: whole cans to buy
3
Paintable area
30 m²
Required paint
6.6 L
US gallons required
1.7435
Imperial gallons required
1.4518
Theoretical unused capacity
0.9 L
Coats
2
Paint coverage starts with the product label
For a rectangular room, wall area is twice the length plus width, multiplied by wall height. Ceiling area is length × width. Doors and windows are subtracted from walls only.
Multiply net area by coats, divide by coverage per litre and then add your allowance. Finish paint and primer remain separate because their coverage can differ. US and imperial gallons have different volumes, so choose the label's gallon family.
Surface texture, absorption and application affect actual usage. The unused capacity is the arithmetic difference after rounding to cans, not a promise of leftover paint.
