What PaintSimple does
The calculator estimates the paint required for the walls of one rectangular room. It uses the room perimeter and wall height, deducts a standard area for doors and windows, applies the selected number of coats and includes 10% extra for normal waste and touch-ups.
Calculation method
The calculator first finds the four-wall area using 2 × (room length + room width) × wall height. It deducts 1.9 m² for each standard door and 1.5 m² for each standard window. The remaining area is multiplied by the coat count, divided by the selected coverage rate and increased by 10%.
Default coverage assumptions
- Smooth, previously painted wall: 11 m² per litre
- New or porous wall: 9 m² per litre
- Rough or textured wall: 7 m² per litre
- Brick or masonry: 6 m² per litre
These are general planning defaults, not claims for a particular product. A coverage rate entered under Advanced settings replaces the selected default.
Designed for beginners
The default experience asks only for information most people already understand: room dimensions, wall condition, coats, doors and windows. Users with a coverage rate from a paint label can enter it under Advanced settings, but it is never required.
What the result means
The result is a planning estimate, not a product guarantee. Paint formulation, wall texture, porosity, preparation, tools and application technique can all change real coverage. Always check the manufacturer’s instructions before buying or applying paint.
Independent and transparent
PaintSimple is an independent educational tool and is not affiliated with a paint manufacturer. The calculator explains its assumptions so users can understand what affects the result.