Drywall calculator
Sheets, mud, tape and screws for one room. The material people forget is the mud — one bucket does not go as far as it looks.
- Board area
- — ft²
- Joint compound
- —
- Tape
- —
- Screws
- —
How the calculation works
walls = 2 × (length + width) × height
Subtract 21 ft² per door and 15 ft² per window, add the ceiling, apply waste, divide by the sheet area.
sheets = area × (1 + waste) ÷ sheet ft²
Consumables use the standard trade ratios: 0.009 gal of compound per ft² of board (a 4.5 gal bucket covers roughly 500 ft² over three coats), tape at 1 ft per 2 ft², and 32 screws per 4 × 8 sheet.
Worked example
12 × 10 ft room, 8 ft walls: perimeter 44 ft × 8 = 352 ft². One door and two windows remove 51 ft², leaving 301 ft². Ceiling adds 120 ft² → 421 ft². With 10% waste, 463 ft² ÷ 32 = 14.5, so 15 sheets. Mud: 421 × 0.009 = 3.8 gal → 1 bucket. Tape: 211 ft. Screws: 480.
Which thickness where
| Location | Thickness | Reason |
|---|---|---|
| Walls, standard | 1/2 in | Code minimum in most areas |
| Ceilings, 16 in joists | 1/2 in | Sag risk is low at 16 in |
| Ceilings, 24 in joists | 5/8 in | Prevents sag between joists |
| Garage / fire separation | 5/8 in Type X | Fire rating |
| Bathrooms, wet walls | 1/2 in moisture-resistant | Paper face resists humidity |
Frequently asked
Do I hang the ceiling first?
Yes. Ceiling sheets go up first so the wall sheets can support their edges, which is what keeps the ceiling joints from cracking.
How many coats of mud?
Three: tape coat, fill coat, finish coat. The calculator assumes that standard, which is where the 0.009 gal/ft² figure comes from.
Should I subtract the door opening?
Yes for material, no for hanging. The opening is covered by a sheet that gets cut out, but you still buy that square footage — which is why waste is set to 10% rather than 5% in rooms with several openings.