Paint Calculator

About this calculator

Paint quantity is area times coats, divided by how many square feet one litre covers in one coat. The room mode builds the wall area from the perimeter and the height, then takes off doors and windows. A door of about 21 sq ft and a window of about 15 sq ft are the defaults. Measure yours if they are different.

Include the ceiling only when you will paint it. It is a large extra area and it changes the order.

The coverage box starts at 120 square feet per litre per coat because that is a common planning figure for interior emulsion. Economy paints and textured walls cover less. The number on the tin replaces the default.

The suggested tins are a simple split into 20 L, 10 L, 4 L, and 1 L sizes. A shop may not stock that split, and you may prefer fewer tins. The litres matter more than the split.

Paint quantity

Wall area = 2 × (length + width) × height
Ceiling = length × width, if you include it
Paintable area = walls + ceiling − door areas − window areas
Litres = paintable area × coats ÷ coverage per litre per coat

Example: 12 × 10 × 10 ft room

Walls of a 12 ft by 10 ft room with 10 ft height are 440 sq ft. One door at 21 sq ft and one window at 15 sq ft leave 404 sq ft.

Two coats at 120 sq ft per litre need 6.73 litres.

404 sq ft of walls, 2 coats, 120 sq ft/L

Ceiling not included.

6.73 litres

How to use

1. Choose a room, or choose an area you have already measured.
2. For a room, enter length, width, and height in feet.
3. Tick the ceiling only if you will paint it.
4. Adjust the door and window counts and their areas.
5. Set coats and the coverage printed on your paint tin.
6. Press Calculate.

Important notes

• Coverage of 120 sq ft per litre per coat is a planning default. The tin you buy is the authority.
• Dark colours and a change of colour use more paint.
• Rough plaster drinks more than a smooth repaint.
• The tin split is one way to buy the litres, not a brand recommendation.

FAQ