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Drywall Calculator
Add each room with its length, width, wall height, doors and windows, and say if the ceiling gets board. Pick the sheet size and a waste percent. You get the sheets to buy, the boxes of joint compound and the screws. A 14 × 12 ft room needs 19 sheets of 4 × 8.
Updated · Sources re-checked by
Walls 380 sq ft, ceiling 168 sq ft
19 sheets of 4 × 8 ft
| Walls | 380 sq ft |
| Ceilings | 168 sq ft |
| Total board | 548 sq ft |
| Joint compound (4.5 gal boxes) | 2 |
| Screws | about 608 (32 per sheet) |
Compound coverage and screw spacing are estimates. Follow the board maker's and compound maker's instructions. Nothing you type is saved or sent anywhere.
How the drywall calculator works
Wall area = 2 × (length + width) × height, minus 21 sq ft per door and 15 per window. Ceiling area = length × width. Sheets = total area ÷ the sheet's area (a 4 × 8 is 32 sq ft), plus the waste percent, rounded up. Joint compound boxes = board area ÷ 450 sq ft, which is the usual rating of a 4.5 gallon box of ready-mix; read your label. Screws per sheet = framing lines across the sheet (the width ÷ stud spacing + 1) × (sheet length ÷ screw spacing), times the sheets. This is an estimate, not a fastening schedule.
| Sheet | Area | Sheets |
|---|---|---|
| 4 × 8 ft | 32 sq ft | 18 |
| 4 × 10 ft | 40 sq ft | 14 |
| 4 × 12 ft | 48 sq ft | 12 |
| Board area | Boxes |
|---|---|
| 250 sq ft | 1 |
| 500 sq ft | 2 |
| 1,000 sq ft | 3 |
| 2,000 sq ft | 5 |
Worked example: a 14 × 12 ft room, 8 ft walls, one door, one window, ceiling too
- Walls: 2 × (14 + 12) × 8 = 416 sq ft, minus 21 for the door and 15 for the window leaves 380 sq ft.
- Ceiling: 14 × 12 = 168 sq ft. Total board: 548 sq ft.
- Sheets of 4 × 8: 548 ÷ 32 = 17.1. With 10% waste: 18.8, so 19 sheets.
- Joint compound: 548 ÷ 450 = 1.2, so 2 boxes.
- Screws: 4 lines × 8 per line = 32 per sheet, 32 × 19 = 608 screws.
Common questions
How many sheets of drywall do I need?
Divide the wall and ceiling area by the area of one sheet, then add about 10% for cuts and mistakes. A 4 × 8 sheet is 32 sq ft.
Should I subtract doors and windows?
Yes, but many people leave out only the large ones. This calculator takes 21 sq ft for a door and 15 for a window, and the waste percent covers the offcuts.
Which sheet size is best?
Longer sheets mean fewer joints to tape, but they are heavier and harder to carry. A 4 × 12 sheet can run the whole length of a wall, a 4 × 8 is easiest to handle.
How much joint compound do I need?
A 4.5 gallon box of ready-mix is commonly rated at about 450 sq ft of board, and USG's rule of thumb is about two boxes per 1,000 sq ft. Check the label of your compound, since lightweight and all-purpose types vary.
How many screws per sheet?
It depends on the stud spacing and the screw spacing you use. A 4 × 8 sheet on studs 16 in apart with screws every 12 in takes about 32. Follow the board maker's fastening guide.
How much waste should I allow?
Ten percent is common for a simple room. Rooms with many corners, angles or short walls can need more, so raise the number.
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Sources
- USG: about two 4.5 gallon boxes of ready-mix joint compound finish 1,000 sq ft of wallboard (checked October 28, 2026)
- Drywall: standard sheet sizes and how the boards are made (checked October 28, 2026)
This calculator is an estimate for planning. Fastening, board thickness and joint compound use depend on the board maker and your local rules, so follow their instructions.