Measuring a room for drywall
- Measure the length and width of the room at floor level, and the wall height from floor to ceiling framing.
- Count the doors and windows. The calculator subtracts about 21 ft² per door (3 × 7 ft) and 15 ft² per window (3 × 5 ft) as rules of thumb. For big openings, like a patio door or a wide archway, subtract the real size instead by reducing the room dimensions or adding fake "windows".
- Decide on the ceiling. Drywalling a ceiling adds length × width, and it's usually hung first.
Many hangers don't subtract small windows at all: the offcuts rarely get reused, and the waste allowance covers them. If you want a conservative order, set doors and windows to 0.
How sheets are calculated
Wall area = 2 × (length + width) × height. Add length × width for the ceiling, subtract the openings, and add waste. Sheets = area ÷ sheet area (32, 40 or 48 ft²), rounded up. A 12 × 12 ft room with 8 ft walls, a ceiling, one door and two windows has 477 ft² to cover. That's 17 sheets of 4 × 8 with 10% waste.
Sheets for common room sizes
| Room | Net area | 4 × 8 sheets | 4 × 12 sheets |
|---|---|---|---|
| 10 × 10 ft | 369 ft² | 13 | 9 |
| 10 × 12 ft | 421 ft² | 15 | 10 |
| 12 × 12 ft | 477 ft² | 17 | 11 |
| 12 × 14 ft | 533 ft² | 19 | 13 |
| 14 × 16 ft | 653 ft² | 23 | 15 |
| 16 × 20 ft | 845 ft² | 30 | 20 |
| Room | Net area | 1.2 × 2.4 m sheets | 1.2 × 3.0 m sheets |
|---|---|---|---|
| 3 × 3 m | 33.1 m² | 13 | 11 |
| 3 × 3.6 m | 37.8 m² | 15 | 12 |
| 3.6 × 3.6 m | 42.8 m² | 17 | 14 |
| 3.6 × 4.2 m | 47.8 m² | 19 | 15 |
| 4.2 × 4.8 m | 58.6 m² | 23 | 18 |
| 4.8 × 6 m | 75.9 m² | 29 | 24 |
Tape, compound and screws
USG's installation guide includes an estimating table. For every 1,000 ft² of gypsum panels it lists about 370 ft of joint tape, 10 gallons of ready-mixed all-purpose joint compound (9 gallons of a lightweight all-purpose type) and 2.7 lb of Type W screws, assuming screws spaced 12 in on ceilings and 16 in on walls. The calculator scales those figures to your sheet count. For the 12 × 12 room above, that's 201.3 ft of tape and 5.44 gal of compound. USG notes compound coverage varies widely with the substrate, tools and technique, so treat it as a starting point.
Which sheets to buy
| Situation | Typical choice | Why |
|---|---|---|
| Walls on studs 16 in on centerWalls on studs 40.6 cm on center | ½ in regular1.3 cm regular | The standard residential wall board |
| Ceilings, joists 24 in on centerCeilings, joists 61 cm on center | ⅝ in, or ½ in sag-resistant/ceiling board1.6 cm, or 1.3 cm sag-resistant/ceiling board | USG lists ⅝ in (long edges across joists) or its ½ in ceiling board for 24 in framingUSG lists 1.6 cm (long edges across joists) or its 1.3 cm ceiling board for 61 cm framing |
| Bathrooms (not wet areas) | Moisture/mold-resistant board | Better in humid rooms. Tile backer goes in showers. |
| Fire-rated assemblies (e.g. garage/house separation) | ⅝ in Type X or as code requires1.6 cm Type X or as code requires | Code sets the rating. Check local requirements. |
Sheet size: longer sheets (10 or 12 ft) mean fewer butt joints, which are the hardest to finish. They're also heavier and harder to get through doors and up stairs. A 4 × 12 sheet of ½ in board is a two-person carry.
Worked examples
Bedroom, 12 × 14 ft, 8 ft walls, ceiling, 1 door, 2 windowsBedroom, 3.66 × 4.27 m, 2.44 m walls, ceiling, 1 door, 2 windows
Room length 14 ft · Room width 12 ft · Wall height 8 ft · Doors 1 · Windows 2 · Include ceiling Yes · Door size 21 ft² · Window size 15 ft² · Sheet area 32 ft² · Waste / overage 10 %Room length 4.27 m · Room width 3.66 m · Wall height 2.44 m · Doors 1 · Windows 2 · Include ceiling Yes · Door size 1.95 m² · Window size 1.39 m² · Sheet area 2.97 m² · Waste / overage 10 %
- Drywall sheets: 19
- Net area to cover: 533 ft²Net area to cover: 49.5 m²
- Joint tape (USG: 370 ft per 1,000 ft²): 225 ftJoint tape (USG: about 1.2 m per m²): 68.6 m
- All-purpose joint compound (USG: 10 gal per 1,000 ft²): 6.08 galAll-purpose joint compound (USG: about 0.41 L per m²): 23 L
- Type W screws (USG: 2.7 lb per 1,000 ft²): 1.6 lbType W screws (USG: about 13 g per m²): 0.74 kg
Basement rec room, 24 × 16 ft, walls only, 4 × 12 sheetsBasement rec room, 7.32 × 4.88 m, walls only, 4 × 12 sheets
Room length 24 ft · Room width 16 ft · Wall height 8 ft · Doors 2 · Windows 2 · Include ceiling No · Door size 21 ft² · Window size 15 ft² · Sheet area 48 ft² · Waste / overage 10 %Room length 7.32 m · Room width 4.88 m · Wall height 2.44 m · Doors 2 · Windows 2 · Include ceiling No · Door size 1.95 m² · Window size 1.39 m² · Sheet area 4.46 m² · Waste / overage 10 %
- Drywall sheets: 14
- Net area to cover: 568 ft²Net area to cover: 52.8 m²
Garage walls only, 22 × 22 ft, 9 ft high, 2 doorsGarage walls only, 6.71 × 6.71 m, 2.74 m high, 2 doors
Room length 22 ft · Room width 22 ft · Wall height 9 ft · Doors 2 · Windows 0 · Include ceiling No · Door size 21 ft² · Window size 15 ft² · Sheet area 48 ft² · Waste / overage 10 %Room length 6.71 m · Room width 6.71 m · Wall height 2.74 m · Doors 2 · Windows 0 · Include ceiling No · Door size 1.95 m² · Window size 1.39 m² · Sheet area 4.46 m² · Waste / overage 10 %
- Drywall sheets: 18
- Net area to cover: 750 ft²Net area to cover: 69.7 m²
A garage overhead door opening is much larger than 21 ft². Reduce the wall length to account for it.A garage overhead door opening is much larger than 1.95 m². Reduce the wall length to account for it.
Hanging tips that save sheets
- Hang the ceiling first, then the walls, with the top sheet tight to the ceiling.
- On walls, run sheets horizontally where you can. That usually means fewer and shorter joints.
- Plan sheets so butt joints are staggered and away from the middle of the wall, where light shows them most.
- Keep large offcuts for closets, soffits and small wall sections.
- Wear eye protection when cutting and a dust mask when sanding joint compound.
Checked against
Each case below is re-run against the calculator by our automated test suite.
| Case | Our result | Checked against | Result |
|---|---|---|---|
| 12 × 12 × 8 ft room with ceiling, 1 door, 2 windows: net area | 477 ft² | Hand calculation | Match |
| Type W screws for 1,000 ft² of board | 2.7 lb | USG J371 installation guide (fastener estimating table) | Match |
| Case | Our result | Checked against | Result |
|---|---|---|---|
| 3.66 × 3.66 × 2.44 m room with ceiling, 1 door, 2 windows: net area | 44.3 m² | Hand calculation | Match |
Frequently asked questions
How many sheets of drywall for a 12 × 12 room?
With 8 ft walls, a ceiling, one door and two windows, about 17 sheets of 4 × 8 with 10% waste.
How many sheets of drywall per bucket of mud?
USG's table gives about 10 gallons of all-purpose compound per 1,000 ft² of board, which is roughly one 4.5–5 gallon pail for every 14–16 sheets of 4 × 8. It varies a lot with technique.
How much drywall for 1,000 square feet of wall?
1,000 ÷ 32 = 32 sheets of 4 × 8 before waste, or about 35 with 10%.
Should I subtract windows and doors?
Subtract large openings. Many pros ignore small windows because offcuts are rarely reusable.
Sources & assumptions
The results are planning estimates, and the cost figures only use prices you enter. Product yields, densities and coverage rates vary, so check the label or ask your supplier, and follow local codes. Figures marked "approximate" or "rule of thumb" are general practice, not exact standards.
- USG Sheetrock Brand Installation and Finishing Guide (J371): fastener, compound and tape estimating table
- USG Drywall–Wood Framed Systems (SA924)
See how we calculate and test our formulas and the changelog. Last updated 2026-10-08.
Reviewed by the MaterialWhiz Editorial Team. This estimate uses the assumptions shown in the calculator. Review the result against your supplier's product coverage and site conditions. Last reviewed: October 10, 2026. See how we calculate · Report a correction.