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Drywall is sold by the sheet, so the Drywall Calculator turns a room into square feet and then into whole sheets. The walls are the perimeter times the wall height, 2 × (length + width) × height, less a typical 15 sq ft per window and 20 sq ft per door; the ceiling is length × width. Each surface gets a waste allowance, usually 10%, and is divided by the sheet area: 32 sq ft for a 4 × 8, 40 for a 4 × 10, 48 for a 4 × 12 and 54 for a 54 in × 12 ft sheet, with walls and ceiling rounded up separately. Weight uses USG's nominal 1.25 lb per sq ft for 1/2 in Sheetrock UltraLight panels, so a 4 × 8 sheet is about 40 lb. The finishing materials use USG's published coverage: about 10 gallons of All Purpose joint compound and 370 ft of paper tape per 1,000 sq ft, and screws at USG's maximum spacing of 16 in on walls and 12 in on ceilings. A 12 × 12 ft room with 8 ft walls and its ceiling is 528 sq ft: 14 wall sheets and 5 ceiling sheets, 19 in all.
| Room | Area | Sheets (walls + ceiling) | Mud pails | Screws |
|---|---|---|---|---|
| 10 × 10 ft, 8 ft walls | 420 sq ft | 15 (11 + 4) | 1 | 448 |
| 10 × 12 ft, 8 ft walls | 472 sq ft | 18 (13 + 5) | 2 | 539 |
| 12 × 12 ft, 8 ft walls | 528 sq ft | 19 (14 + 5) | 2 | 567 |
| 12 × 14 ft, 8 ft walls | 584 sq ft | 21 (15 + 6) | 2 | 630 |
| 14 × 16 ft, 8 ft walls | 704 sq ft | 25 (17 + 8) | 2 | 756 |
| 12 × 12 ft, 9 ft walls | 576 sq ft | 20 (15 + 5) | 2 | 595 |
| 20 × 20 ft, 8 ft walls | 1040 sq ft | 36 (22 + 14) | 3 | 1,106 |
Android: Smart Drywall Calculator on Google Play. iPhone: the drywall calculators are inside Roofing Calculator & Estimator on the App Store.
Add the wall area — perimeter × height — and the ceiling area if you are covering it, subtract large openings, add about 10% for cuts and divide by the sheet size: 32 sq ft for a 4 × 8, 40 for a 4 × 10, 48 for a 4 × 12. Walls and ceiling are counted separately and each rounded up. A 12 × 12 ft room with 8 ft walls is 384 sq ft of wall and 144 of ceiling: 14 + 5 = 19 sheets of 4 × 8.
19 sheets of 4 × 8 ft for the walls and ceiling with 10% waste (14 for the 8 ft walls, 5 for the ceiling), or 14 sheets for the walls alone. With 4 × 12 sheets it is 9 for the walls and 4 for the ceiling.
USG lists its 1/2 in Sheetrock UltraLight panels at 1.25 lb per sq ft, so a 4 × 8 sheet is about 40 lb and a 4 × 12 about 60 lb. USG's 3/8 in panels are 1.4 lb per sq ft and 1/4 in panels 1.2 lb per sq ft (nominal figures from the USG submittal sheets).
Longer sheets mean fewer butt joints to tape, and butt joints are the hardest to hide. 4 × 12 sheets hung horizontally run the full length of most walls, but they weigh about 60 lb each in 1/2 in UltraLight and need two people and a clear path into the room. 4 × 8 sheets are easier to carry and fit in a car.
Subtract doors and large openings; many hangers sheet straight over small windows and cut them out, then use the offcut elsewhere. The calculator deducts a typical 15 sq ft per window and 20 sq ft per door from the walls, then adds the waste allowance.
Finishing the room? The drywall mud calculator turns the same square footage into pails of joint compound and rolls of tape.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.