Paint Calculator

Estimate how much paint is needed to cover the walls and ceiling of a room. Enter the room dimensions, deduct doors and windows, choose how many coats you plan to apply, and get the total litres (or gallons) of paint required.

Enter room details

Units
Each door is treated as ≈ 1.8 m² (20 ft²).
Each window is treated as ≈ 1.5 m² (16 ft²).
Default: 10 m² per litre (or 350 ft² per gallon). Check the tin for exact figure.
Surfaces to paint

Enter room details, then press Calculate paint.

Paint quantity formulas

Wall area = perimeter × height − door area − window area

Perimeter = 2 × (length + width)

Paint needed = (surface area × coats) ÷ coverage per litre (or gallon)

Default coverage: 10 m² per litre (metric) or 350 ft² per gallon (imperial). Coverage varies by product and surface texture.

Wall Area Calculator

Just the wall area with deductions.

Square Footage Calculator

Room area calculator.

Frequently asked questions

Two coats give better coverage, hide brush strokes and give the colour its true depth. Some premium paints claim one-coat coverage, but a second coat generally extends durability and appearance.

Buy about 10% more than the calculated amount. This covers spills, touch-ups and any minor underestimation of surface area. Leftover paint kept properly can be reused for future repairs, though check the tin's shelf-life guidance.