Paint Coverage Calculator for Decorators

The paint coverage calculator estimates how much paint you need for a decorating job. Enter your wall, ceiling or woodwork measurements along with the number of coats and the paint coverage rate, and the calculator works out the total paintable area, the litres of paint required and a recommended number of tins.

Choose whether you are painting walls, ceilings or woodwork using the tabs. Enter the number of walls and their dimensions. The calculator automatically deducts standard door and window openings on the walls tab — you can adjust these sizes if your openings are different. Enter the number of coats, your paint coverage rate (check the tin) and your preferred tin size. Add a wastage allowance if you want a buffer.

Total wall area is the combined width × height of all walls. Standard door and window areas are deducted to give a net paintable area. Paint required in litres is calculated as (net area × number of coats) ÷ coverage per litre. A wastage allowance is added on top. The calculator then recommends the most efficient combination of tins to cover the required litres.

Porous or bare surfaces may need more paint, particularly on the first coat. Textured walls, dark colour changes and application method (brush, roller or spray) all affect coverage. Always check the manufacturer's coverage guidance on the tin and consider the surface condition before ordering.