Drywall / Plasterboard Calculator
By Santaji GadepatilinUpdated October 27, 2026
Drywall (plasterboard) is sold in standard sheets. Knowing the wall and ceiling area tells you how many sheets, screws and joint compound you need. This free drywall / plasterboard calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the drywall / plasterboard calculator
Enter the total area of walls and ceilings and choose the sheet size. The number of sheets with waste is calculated.
Example
60 m² with 2400 × 1200 mm sheets and 10% waste:
60 × 1.1 ÷ 2.88 = 23 sheets
Sheets needed by room size
Walls only, 2.4 m ceiling, 1.2 × 2.4 m sheets (2.88 m²), 10% waste:
| Room | Wall area (approx.) | Sheets |
|---|---|---|
| 3 × 3 m | 28.8 m² | 11 |
| 3 × 4 m | 33.6 m² | 13 |
| 4 × 4 m | 38.4 m² | 15 |
| 4 × 5 m | 43.2 m² | 17 |
| 5 × 6 m | 52.8 m² | 21 |
Add the ceiling area (length × width) if you are boarding that too.
Standard sheet sizes
| Size | Area |
|---|---|
| 1200 × 2400 mm | 2.88 m² |
| 1200 × 2700 mm | 3.24 m² |
| 4 × 8 ft | 32 ft² |
| 4 × 12 ft | 48 ft² |
Longer sheets reduce joints on tall walls and ceilings.
Other materials
| Material | Rough quantity per 100 m² of board |
|---|---|
| Screws | about 1,000–1,200 (at 300 mm centres) |
| Joint tape | about 120–140 m |
| Joint compound | about 40–50 kg (ready-mixed) |
Board types
- Standard: dry areas.
- Moisture-resistant (often green): bathrooms and kitchens.
- Fire-rated (often pink or red): garages, escape routes and where codes require.
- Sound-rated: party walls and bedrooms.
Measuring walls
Wall area = room perimeter × wall height. For a 5 × 4 m room with 2.4 m walls: 18 × 2.4 = 43.2 m², plus the ceiling of 20 m².
Frequently asked questions
How many drywall sheets do I need?
Divide the total area by the sheet area and add about 10% for cuts and openings.
Should I subtract doors and windows?
For large openings, yes. Small windows are often ignored because the offcuts are rarely reusable.
How many screws per sheet?
Roughly 30–40 screws for a 2400 × 1200 mm sheet on studs at 600 mm centres.
How many sheets of drywall do I need for a 12 × 12 room?
With 8 ft walls, the walls are about 384 sq ft — 12 sheets of 4 × 8 ft plus 10% waste, or 13–14 sheets. Add 5 sheets for the ceiling.
Should I subtract doors and windows?
Subtract large openings, but many installers leave small windows in the calculation to cover waste and offcuts.