Paint & Walls calculators

One set of measurements, three calculators

All three tools start from the same numbers: the length and width of the room and the height of the walls. The perimeter multiplied by the height gives the wall area, and doors and windows come off that total. Measure at floor level with a tape, round each figure up to the next inch or centimetre, and note the sizes of any unusually large openings such as patio doors.

The usual order of work

1. Drywall or plasterboard goes up first, followed by tape and joint compound, sanding and a final skim.
2. Primer seals new boards and patched areas so the finish coat dries evenly.
3. Paint or wallpaper comes last. Lining paper is sometimes hung first on uneven walls before wallpaper.

Ceilings count too

A ceiling is roughly the same area as the floor beneath it, and it often takes a different paint and its own coat of primer. Decide early whether ceilings are part of the job, because they change the drywall sheet count, the joint compound and the paint order more than any other single choice.

Terms that differ between countries

North Americans say drywall, sheetrock or gypsum board; in the UK it is plasterboard, and joint compound is often called filler or jointing compound. UK wall paint is usually sold as emulsion in litre tins, while US and Canadian stores sell gallon and quart cans. The calculators accept either system and convert your numbers when you switch.