How to use the drywall calculator
- Choose Imperial or Metric. The sheet list changes to match common sizes, and you can still choose any size.
- Add one row per wall with its length and height.
- Enter the ceiling area if you are boarding the ceiling too.
- Enter the total door and window area to subtract.
- Choose the sheet size and set the waste allowance.
- Adjust the screws, compound and tape assumptions to match the products you are using.
- Enter unit prices in the takeoff table for a cost estimate.
How the estimate works
Net area = sum of wall areas + ceiling area − openings. Sheets = net area ÷ sheet area × (1 + waste), rounded up. Screws = sheets × screws per sheet. Compound and tape are the net area multiplied by the per-square-metre rates you set. Because those rates vary by product and finish, they are shown as assumptions rather than fixed figures.
Worked examples
US bedroom. Walls of 12, 10, 12 and 10 ft, all 8 ft high: 352 ft². Subtract 38 ft² for a door and window: 314 ft². With 4 × 8 ft sheets and 10% waste: 11 sheets and 330 screws.
European room. Walls of 4, 3, 4 and 3 m at 2.5 m high: 35 m². Subtract 3.5 m² for openings: 31.5 m². With 1,250 × 2,500 mm boards (3.125 m²) and 10% waste: 12 boards.
How to interpret the results
The sheet count is what you buy. The compound and tape figures are only a starting point; buy one extra pack rather than run out halfway through a coat.
Tips and common mistakes
- Choose the tallest sheet that fits your wall height to avoid horizontal joints.
- Hang ceilings first, then walls, so wall sheets support the ceiling edges.
- Check the fire, moisture or sound rating your project needs; specialist boards come in fewer sizes.
- Stagger joints between layers and on opposite sides of a wall.
Assumptions and limitations
The calculator works with areas, not a cutting plan, so very complex rooms with many openings may need more waste. Fire-rated assemblies must follow the tested system and your local code.