Drywall Calculator
Sheets = (wall + ceiling area) ÷ 32 sq ft per sheet
How Drywall Calculations Work
Drywall (gypsum board) is sold in 4×8 sheets covering 32 sq ft each. Wall area = 2 × (length + width) × height. A 12 ft × 12 ft room with 8 ft ceilings has 384 sq ft of wall. Add ceiling (144 sq ft) if finishing overhead for 528 sq ft gross. Subtract openings: one door (21 sq ft) and two windows (24 sq ft) = 483 sq ft net.
Add 10% waste for cuts around outlets and corners: 483 × 1.10 = 531 sq ft. Sheets needed = 531 ÷ 32 = 16.6 — round up to 17 sheets. Joint compound averages 0.5 gallons per sheet for taping and two finish coats. Tape runs roughly 24 linear feet per sheet along seams and corners — 17 × 24 = 408 ft of paper or mesh tape.
Sheet thickness depends on application: 1/2 in is standard for walls; 5/8 in for ceilings (reduces sag at 16 in OC framing) and fire-rated assemblies. Moisture-resistant (green board) goes in bathrooms; Type X for fire barriers. Screw spacing is 12 in on walls, 8 in on ceilings — plan 30–40 screws per sheet.
Finishing levels range from Level 1 (fire taping only) to Level 5 (skim coat for gloss paint). Most residential interiors use Level 4 — two coats compound, sanded smooth. Pair results with the paint calculator once surfaces are finished.
| Room | Net Area | Sheets (10% waste) |
|---|---|---|
| 10×12 ft, 8 ft, ceiling included | ~411 sq ft | 15 sheets |
| 12×12 ft, 8 ft, ceiling included | ~483 sq ft | 17 sheets |
| 14×16 ft, 9 ft, walls only | ~468 sq ft | 17 sheets |
| 20×15 ft, 8 ft, ceiling included | ~660 sq ft | 23 sheets |
Enter room dimensions, door and window counts, and whether to include the ceiling for sheet, compound, and tape quantities. Follow up with the paint calculator for finishing.
Examples
| Example | Result |
|---|---|
| 12×12 ft, 8 ft, 1 door, 2 windows, with ceiling | 17 sheets, 8.5 gal compound |
| 10×14 ft, 8 ft, walls only | ~12 sheets |
| 14×16 ft, 9 ft, ceiling included | ~20 sheets |
| 20×15 ft great room, 10 ft ceilings | ~28 sheets |
| 8×10 ft bathroom remodel | ~8 sheets |
| 12×18 ft garage, 8 ft, no openings | ~16 sheets |
| 16×20 ft addition, 9 ft, 2 doors, 4 windows | ~24 sheets |
Frequently asked questions
A standard 4×8 sheet covers 32 sq ft. 4×12 sheets cover 48 sq ft and reduce seams on long walls but are heavier and harder to handle solo.
1/2 inch is standard for walls. Use 5/8 inch on ceilings (less sag) and where fire codes require Type X rated board.
Budget about 0.5 gallons of joint compound per 4×8 sheet for taping and two finish coats. Texture or skim coating needs more.