Drywall Calculator
Calculate how many drywall sheets you need for a wall or ceiling, based on area, standard sheet size and waste.
How to use the drywall calculator
- Enter the total wall length (sum of all walls) and the wall height.
- Choose the sheet size you plan to use.
- Enter your desired waste percentage — 10% is common for simple rooms with straight walls.
How the sheet count is calculated
The calculator adds waste to the area, then divides by the area of a single sheet:
A common drywall sheet size is 1200 × 2400 mm, giving 2.88 m² per sheet. If you're covering walls with many corners, doors or windows, it can pay off to increase the waste percentage somewhat.
Moisture and fire — why several board types exist
Standard plasterboard does not tolerate sustained moisture. Wet rooms therefore use dedicated moisture-resistant boards, and in the shower zone itself a membrane is required on top of the board — the board alone is not a moisture barrier. In rooms with fire resistance requirements, fire-rated board is used, which contains additives and reinforcement that hold the board together longer in a fire.
Board type also affects installation. Heavy boards need closer screw spacing and often two people to lift, and some assemblies require two layers with staggered joints to achieve the documented fire or acoustic rating. This calculator works out the number of boards from the area — which type and how many layers are required follows from the room's function and from building regulations.
Frequently asked questions
Should I subtract area for doors and windows?
For large openings (big window walls, double doors) it can be worth it. For regular doors and windows it's often simpler to just plan for a bit extra waste, since cut-off scraps often can't be reused elsewhere.
Do I need two layers of drywall on fire-rated walls?
Yes, fire-separation walls often require two layers of drywall. Check the requirements in your local building code or with a professional, and double the sheet count if needed.