Drywall Calculator (Plasterboard)
How many sheets of drywall or plasterboard for a room, with screws.
Good to know. Hang the ceiling first, then the walls. The wall sheets hold up the ceiling edges.
Approximate. Real-world values vary.
How it works
In plain words
The wall area is the room’s perimeter times its height, minus about 2 m² (21 ft²) for each door and 1.5 m² (16 ft²) for each window. Add the ceiling, add the waste allowance, and divide by the area of one sheet. Allow about one screw per square foot of board.
The formula
walls = 2 × (length + width) × height − openings area = walls + ceiling sheets = ⌈area × (1 + waste) ÷ sheet area⌉
Worked example
The walls are 2 × (4 + 3) × 2.4 = 33.6 m², minus 3.5 m² for a door and a window: 30.1 m². With the 12 m² ceiling and 10% extra, 46.3 m² ÷ 2.88 m² is 17 sheets.
Sources
No outside data or rates: this is plain arithmetic.
2 automated tests check its answers on every change.
About the drywall calculator (plasterboard)
Drywall, called plasterboard in the UK and gypsum board elsewhere, is sold in standard sheets: 4 × 8 ft and 4 × 12 ft in the US, 1200 × 2400 mm in the UK, Europe and Australia. This calculator works out how many sheets cover a room’s walls and ceiling.
Enter the room’s size and ceiling height, and how many doors and windows it has. The calculator takes about 2 m² (21 ft²) for each door and 1.5 m² (16 ft²) for each window off the wall area. For unusually large windows or patio doors, measure them and reduce the length instead.
Add 10% for waste on straightforward rooms and 15% for rooms with many corners, openings or sloped ceilings. Longer sheets mean fewer joints to tape and fill: 12 ft sheets or 2700 mm boards are worth it on long walls and high ceilings, if you can get them through the door.
Plan on about one screw per square foot of board, 32 for a 4 × 8 sheet, and a roll of joint tape and a bucket of joint compound for every few sheets. Use moisture-resistant board in bathrooms and fire-rated board where building rules require it, such as between a garage and a house.
Questions people ask
How many sheets of drywall do I need for a 12 × 12 room?
With 8 ft ceilings, about 12 sheets of 4 × 8 for the walls and 5 for the ceiling, before openings, plus 10% for waste.
How many screws per sheet of drywall?
About 32 for a 4 × 8 ft sheet: one per square foot, at 16 in (40 cm) along each stud or joist.
What size is a sheet of plasterboard?
Usually 1200 × 2400 mm in the UK and Europe, and 4 × 8 ft (1219 × 2438 mm) in the US.