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Drywall Calculator
Enter the total area of walls and ceilings you are covering to get sheet counts in both standard sizes. A 4×8 sheet covers 32 square feet and a 4×12 covers 48, and the waste allowance covers cuts, openings and the occasional damaged corner.
Results update as you type. Estimates only — confirm final quantities before ordering.
The formula
4×8 sheet = 32 ft² • 4×12 sheet = 48 ft²
Sheet counts are rounded up to whole sheets. For a room, the area is the walls (perimeter × ceiling height) plus the ceiling (length × width) if you are hanging that too. Most estimators do not deduct standard doors and windows — the waste allowance absorbs them.
Worked example
Example: a 12 ft × 12 ft room with 8 ft ceilings, walls and ceiling, 10% waste.
- Walls: 4 walls × 12 ft × 8 ft = 384 ft²; ceiling: 12 × 12 = 144 ft²; total 528 ft²
- With waste: 528 × 1.10 = 580.8 ft²
- 4×8 sheets: 580.8 ÷ 32 = 19 sheets | 4×12: 580.8 ÷ 48 = 13 sheets
Reference chart
| Area to cover | 4×8 sheets | 4×12 sheets |
|---|---|---|
| 100 ft² | 4 | 3 |
| 200 ft² | 7 | 5 |
| 300 ft² | 11 | 7 |
| 500 ft² | 18 | 12 |
| 800 ft² | 28 | 19 |
| 1,000 ft² | 35 | 23 |
Frequently asked questions
How do I calculate the area of a room for drywall?
Walls: add the lengths of all walls (the perimeter) and multiply by ceiling height. Ceiling: length × width. Add the two if you are hanging both. Stairwells and sloped ceilings need their own measurements added in.
Should I use 4x8 or 4x12 sheets?
4×12 sheets cover long walls and ceilings with fewer seams to tape and finish, and pros prefer them where ceilings are 8–12 ft. They are heavier and awkward for one person, so 4×8 remains the DIY standard, especially in tight rooms and stairways.
What thickness of drywall do I need?
1/2 inch is standard for walls. 5/8 inch (Type X) is used for fire-rated assemblies such as garage separation walls and many ceilings. 1/4 inch is for going over existing surfaces and gentle curves, not for new framing.
How much waste should I allow?
Ten percent covers most rectangular rooms. Go to 15% for rooms with many openings, angles, soffits or a first-time installer — a torn or miscut sheet is the most common shortage.
Related calculators
- Paint Calculator — Gallons of paint for a room's walls, by coats.
- Board Foot Calculator — Board feet and lumber cost from thickness, width, length and quantity.
- Tile Calculator — Tiles and boxes needed, with waste for cuts and breakage.
Sources & method: Sheet coverage 4×8 = 32 ft², 4×12 = 48 ft²; estimating waste 10–15% per Gypsum Association practice; cross-checked against Inch Calculator — Drywall Calculator.