How to use this calculator
- Enter the room's length, width and wall height.
- Tick whether the ceiling is included.
- Enter doors and windows, then choose the sheet size you'll buy.
The formula
Area = 2 × (length + width) × height + ceiling − doors − windows
Sheets = area × (1 + extra %) ÷ sheet area, rounded up
The extra covers offcuts around openings and the occasional broken corner. 10 % is common; rooms with many openings or angles need more.
Choose sheets as tall as your walls where you can — fewer horizontal joints means less taping and a better finish.
Worked example
A 4 m × 3 m room with 2.4 m walls and the ceiling, less one door and one window, has 42.2 m² to cover.
With 10% extra and 2.88 m² sheets, you need 17 sheets.
Tips before you buy
- Use moisture-resistant board in bathrooms and fire-rated board where your building rules require it.
- Ceiling boards are heavy — use a board lifter or a second person.
- Screws, joint tape and compound are sold separately; ask your supplier for the right amounts for your sheet count.
Frequently asked questions
›What size is a sheet of drywall?
In the US, 4 × 8 ft (32 ft²) is standard, with 4 × 10 and 4 × 12 ft for taller walls. In the UK, 1200 × 2400 mm (2.88 m²) is most common; in France 1200 × 2500 mm, and in Germany boards are usually 1250 mm wide.
›Should I subtract windows and doors?
Yes, but keep the 10 % extra — cutting around openings creates offcuts that are often too small to reuse.
Sources
- Standard sheet sizes: US 4 × 8/10/12 ft; UK/EU 1200 × 2400/2700 mm.
Formulas last reviewed: September 29, 2026. How we check our formulas