Most manufacturers estimate without subtracting doors and windows, because the offcuts rarely get reused. Tick the box to subtract them if you prefer.
How the drywall calculator works
DrywallCalc adds up the wall area (perimeter × height) and the ceiling area (length × width). If you choose to, it subtracts 20 sq ft for each door (3 ft × 6 ft 8 in) and 15 sq ft for each window (3 × 5 ft). Walls and ceiling are each multiplied by the waste allowance, divided by the sheet area and rounded up to whole sheets.
Compound, tape and screws are worked out on the area you hang, not on the offcuts: 10 gallons of ready-mixed all-purpose compound and 370 ft of paper tape per 1,000 sq ft (USG product data), and 875 screws per 1,000 sq ft of wall and 1,094 per 1,000 sq ft of ceiling (USG Gypsum Construction Handbook, framing 16 in on centre).
Sheets for common rooms
| Room (8 ft walls + ceiling) | Area | 4×8 sheets | 4×12 sheets | Compound | Tape |
|---|---|---|---|---|---|
| 10 × 10 ft | 420 sq ft | 15 | 11 | 4.2 gal | 156 ft |
| 10 × 12 ft | 472 sq ft | 18 | 12 | 4.7 gal | 175 ft |
| 12 × 12 ft | 528 sq ft | 19 | 13 | 5.3 gal | 196 ft |
| 12 × 14 ft | 584 sq ft | 21 | 14 | 5.8 gal | 217 ft |
| 14 × 16 ft | 704 sq ft | 25 | 17 | 7 gal | 261 ft |
| 16 × 20 ft | 896 sq ft | 31 | 22 | 9 gal | 332 ft |
With a 10% waste allowance and no deduction for openings. These are estimates: products and finishing levels differ, so check the coverage on your compound and the fastener schedule your code or board manufacturer requires. Metric: 1 sq ft = 0.0929 m², and a 1200 × 2400 mm sheet covers 2.88 m² (about 31 sq ft).
Frequently asked questions
How many sheets of drywall for a 12×12 room?
About 19 sheets of 4×8 for walls and ceiling with 8 ft walls and 10% waste, or 13 sheets of 4×12.
How much waste should I allow?
About 10% for simple rooms and 15% for rooms with many corners, openings or angled ceilings.
Should I subtract doors and windows?
USG and CertainTeed estimate without deducting them; subtracting gives a tighter count with less spare.
Is DrywallCalc free?
Yes, with no sign-up or ads.
Are my measurements saved?
Yes, in this browser only.