Estimating plasterboard looks simple: area divided by sheet size. But the waste comes from how sheets fit walls, and the consumables are where many estimates fall short.
Measure walls and ceilings
Measure the perimeter and multiply by the wall height. Subtract large openings such as doors, windows and archways, but not small ones: you'll rarely use the offcut from a switch box or a small window. Add the ceiling area if you're boarding it.
Standard deductions: about 1.9 m² per door and 1.5 m² per typical window.
Pick the sheet size
In the UK, 2400 × 1200 mm boards are standard for walls at 2.4 m ceiling height. 1800 × 900 mm or 2400 × 900 mm boards are easier to handle on ceilings and in lofts. Use 12.5 mm on walls and ceilings at 400 or 600 mm centres.
Waste
10–12% covers most rooms. Go higher for rooms with lots of short walls, sloped ceilings or many openings.
Consumables people forget
- Screws: about 25–30 per 2400 × 1200 board at 300 mm centres. Buy boxes of 1,000.
- Finish: a full skim with multi-finish uses roughly one 25 kg bag per 10 m² at 2 mm. Taping and jointing instead uses far less: about 0.4 kg/m².
- Scrim tape: about 1.25 m per m² of board, in 90 m rolls.
- Angle bead for every outside corner and window reveal.
- Adhesive if you're dot-and-dabbing onto masonry.
Labour
Plasterers often price boarding and skimming per m² or per room. Ceilings, stairwells and small rooms like WCs take longer per m².
The plasterboard calculator handles the whole room and the consumables in one pass.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check the Building Regulations and Building Control for your project.