Drywall Calculator
Find how many sheets of drywall you need for the walls and ceiling of a room. Drywall is also called gypsum board or plasterboard, and is sold under brand names such as USG's Sheetrock. Enter the walls, add the ceiling, and subtract doors and windows to see the total area and the number of sheets for each common size.
Add a ceiling or more walls, or subtract doors and windows.
- Choose US or Metric. You can still change the unit of any single field.
- The first section is set to Room walls. Enter the room's Length and Width and the wall Height. For a single wall, choose Rectangle and enter the wall's length as Length and its height as Width.
- Use Add section to add the ceiling or more walls. To leave out doors and windows, add a section for each one, measure it, and set it to Subtract. Use Quantity for several of the same size.
- Check the Waste allowance. It starts at 10%.
- Optionally, enter a Custom sheet width and length for a size not in the table, and a price per sheet or per area to estimate the cost.
The results show the number of sheets for every common size, so you can
compare them or mix sizes. Dimension fields accept whole numbers,
decimals, fractions, and mixed numbers, such as 12,
11.75, 3/4, or 8 1/2.
How many sheets of drywall you need
The calculator adds up the area to cover, adds the waste allowance, and divides by the area of one sheet:
Total area = net area × (1 + waste % ÷ 100)
Sheets = total area ÷ (sheet width × sheet length), rounded up
The walls of a room are the distance around the room times the wall height. Convert every measurement to the same unit before you divide. With several sections, the calculator adds the sections set to Add and subtracts those set to Subtract. The area of each shape is calculated as follows:
| Shape | Area |
|---|---|
| Room walls | 2 × (length + width) × height |
| Rectangle | length × width |
| Circle | π × diameter² ÷ 4 (or π × radius²) |
| Triangle (base and height) | base × height ÷ 2 |
| Triangle (three sides) | Heron's formula: √(s(s − a)(s − b)(s − c)), where s = (a + b + c) ÷ 2 |
| Trapezoid | (parallel side A + parallel side B) ÷ 2 × height |
| Ring | π × (outer diameter² − inner diameter²) ÷ 4 |
| Rectangular border | outer length × outer width − (outer length − 2 × border width) × (outer width − 2 × border width) |
| Known area | the area you enter |
Drywall sheet sizes
The calculator lists these sizes. They are written as width × length, with the area of one sheet in parentheses. Sheets in the UK and Australia are often listed with the length first, such as 2400 x 1200 mm.
| Where | Common sizes |
|---|---|
| US | 4 × 8 ft (32 ft²), 4 × 10 ft (40 ft²), 4 × 12 ft (48 ft²) |
| UK | 900 × 1800 mm (1.62 m²), 1200 × 2400 mm (2.88 m²) |
| Australia | 1200 × 2400 mm (2.88 m²), 1200 × 2700 mm (3.24 m²), 1200 × 3000 mm (3.6 m²) |
Other sizes are made too. USG's Sheetrock Wallboard Estimator offers lengths from 8 to 16 ft and 54 in wide sheets, and Gyprock boards in Australia come in widths of 1200 and 1350 mm and lengths up to 6000 mm. For these, enter the sheet's width and length as a custom sheet.
Extra drywall for waste
Cutting sheets to fit around corners, doors, and windows leaves offcuts, and sheets can break. The UK building materials supplier Building Materials Nationwide says 10% extra is a good general rule, and 15% if you want to be cautious, so the waste allowance starts at 10%. You can change it from 0% to 100%.
USG's Sheetrock Wallboard Estimator does not include an allowance for waste, so its count can be lower than this calculator's for the same area. For rooms with many corners or openings, raise the waste allowance.
Examples
A bedroom
The walls of a room 12 ft × 10 ft with 8 ft walls are 2 × (12 + 10) × 8 = 352 ft². With a 10% waste allowance, the total is 387.2 ft². That is 387.2 ÷ 32 = 12.1, so 13 sheets of 4 × 8 ft, or 387.2 ÷ 48 = 8.07, so 9 sheets of 4 × 12 ft. Adding the ceiling, 12 × 10 = 120 ft², brings the total to 519.2 ft², or 17 sheets of 4 × 8 ft.
Metric dimensions
The walls of a room 4 m × 3.5 m with 2.4 m walls are 36 m², or 39.6 m² with 10% added. That is 39.6 ÷ 2.88 = 13.75, so 14 sheets of 1200 × 2400 mm, or exactly 11 sheets of 1200 × 3000 mm.
FAQ
With 8 ft walls, the walls are 384 ft². With 10% extra, that is 422.4 ft², so 14 sheets of 4 × 8 ft or 9 sheets of 4 × 12 ft. With the ceiling too, the total is 580.8 ft², so 19 sheets of 4 × 8 ft or 13 sheets of 4 × 12 ft.
A 4 × 8 ft sheet covers 32 ft², a 4 × 10 ft sheet 40 ft², and a 4 × 12 ft sheet 48 ft².
With 2.4 m walls, the walls are 38.4 m². With 10% extra, that is 42.24 m², so 15 sheets of 1200 × 2400 mm.
Yes, for this calculator. Sheetrock is USG's brand of gypsum board, or drywall, and comes in the same standard sheet sizes. Gypsum board and plasterboard are other names for the same material.
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