Drywall Calculator
Calculate how many drywall sheets you need. Enter room dimensions and ceiling height, pick a 4x8 or 4x12 sheet, and get the exact sheet count to buy.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Drywall Calculator Works
This calculator estimates how many drywall sheets (also called sheetrock or gypsum board) you need to finish a room. Enter the room length and width, the ceiling height, choose whether to include the ceiling, pick a sheet size, and set a waste percentage. It returns the total surface area, the bare sheet count, and the final number to buy.
It works by computing the wall area from the room’s perimeter and height, optionally adding the ceiling, dividing by the area of one sheet, rounding up to whole sheets, and padding the result with your waste allowance.
The Formula
Wall area (ft²) = 2 × (length + width) × ceiling height Ceiling area (ft²) = length × width (optional) Total area = wall area + ceiling area Sheets = ceil( total area ÷ sheet area ) Sheets to buy = ceil( sheets × (1 + waste% ÷ 100) )
A 4 × 8 ft sheet covers 32 ft², a 4 × 10 ft sheet covers 40 ft², and a 4 × 12 ft sheet covers 48 ft². The count is rounded up because partial sheets cannot be purchased and offcuts are often unusable.
Worked Example
A 14 ft × 12 ft room with 8 ft ceilings, walls only, 4 × 8 ft sheets, and 10% waste:
- Wall area = 2 × (14 + 12) × 8 = 2 × 26 × 8 = 416 ft²
- Sheets = ceil(416 ÷ 32) = 13 sheets
- Sheets to buy = ceil(13 × 1.10) = 15 sheets
If you also drywall the ceiling, add 14 × 12 = 168 ft², for a total of 584 ft² → ceil(584 ÷ 32) = 19 sheets, and 21 sheets with 10% waste.
Choosing Sheet Size and Waste
| Sheet size | Coverage | Best for |
|---|---|---|
| 4 × 8 ft | 32 ft² | Standard rooms, easy to carry |
| 4 × 10 ft | 40 ft² | Taller walls, fewer butt joints |
| 4 × 12 ft | 48 ft² | Long walls, fewest seams |
Larger sheets reduce the number of taped seams, which speeds up finishing and gives a smoother wall, but they are heavier and harder to maneuver up stairs or around tight corners. For most DIY jobs, 4 × 8 ft panels strike the best balance. Add roughly 10% waste for a simple room and up to 15% when there are many cuts, then round up to full sheets so you are not short mid-project.
Frequently asked questions
How do I calculate how much drywall I need?+
Find the total surface area to cover, then divide by the area of one sheet and round up. Wall area = 2 × (length + width) × ceiling height. A 4 × 8 ft sheet covers 32 ft², a 4 × 12 ft sheet covers 48 ft². For a 14 × 12 ft room with 8 ft walls, that is 416 ft² ÷ 32 = 13 sheets before waste.
How many square feet is a sheet of drywall?+
A standard 4 × 8 ft sheet covers 32 ft². A 4 × 10 ft sheet covers 40 ft², and a 4 × 12 ft sheet covers 48 ft². Larger sheets mean fewer seams to tape but are heavier and harder to handle in tight spaces.
Should I subtract doors and windows?+
For a quick estimate you can leave them in, since the extra acts as a waste buffer. For large openings, subtract their area from the total before dividing by the sheet area, then add a 10% waste allowance on top for cuts and breakage.
How much drywall waste should I add?+
Add about 10% for a typical room with standard openings, and up to 15% for rooms with many corners, angles, or small cuts. Waste covers offcuts, damaged sheets, and pieces too small to reuse elsewhere on the job.
Is drywall the same as sheetrock?+
Yes. Sheetrock is a brand name owned by USG that has become a generic term for gypsum drywall panels. The calculation is identical regardless of brand, since all standard panels come in the same 4 ft width and 8, 10, or 12 ft lengths.