Plasterboard calculator

Plasterboard is cheap enough that most people just want the number of sheets and to get on with it, but boarding a room short means an extra trip and a joint in an awkward place. This calculator works out the sheets for a wall or ceiling from the area and your board size. Here's how it's worked out.

How to work out how many sheets you need

Divide the area you're boarding by the area of one sheet, and add wastage for the cuts.

Sheets = area × (1 + wastage) ÷ sheet area.

A standard 1200 by 2400mm sheet covers 2.88 square metres, so a 12 square metre wall needs about five sheets once 10% wastage is added. The calculator works the sheet area out from the size you enter, so it fits whatever boards you're buying.

Plasterboard sheet sizes

The most common sheet is 1200 by 2400mm, covering 2.88 square metres. You'll also see 1200 by 2700mm for taller walls and smaller 900 by 1800mm boards that are easier to handle single-handed. Thickness is usually 12.5mm for walls and ceilings, with 9.5mm on some ceilings. Set the sheet size to match what you're using and the count adjusts.

Walls and ceilings, the same way

A ceiling works exactly like a wall: its area is the room length times the width, so a 4m by 3m room is 12 square metres of ceiling. Put those two dimensions in and the calculator gives you the sheets. For a whole room, work out the walls and the ceiling separately and add them together.

How much wastage to allow

Around 10% covers the cuts around windows, doors, sockets and corners, and the offcuts you can't reuse. A plain, square room wastes less; a room with lots of openings or an awkward shape wastes more, so nudge it up for those. Boards are cheap, so a spare sheet is worth having.

What comes after boarding

Boarding is the first stage. Most walls are then taped and skim-plastered, and once the plaster is dry they're painted, starting with a mist coat on the fresh plaster. Work out the paint for the finished walls with our paint calculator, which handles the coats and the coverage.

From materials to a priced job

Sheets are one line; the labour in fixing, taping and finishing is the rest. Price the whole job with how to price a job so you actually make a profit, and drop the materials into a clean, itemised quote with the quote generator.

This tool is for general estimating and gives approximate quantities. Board sizes and room shapes vary, so check your own measurements, and order a sensible amount over rather than exactly to the calculation.