How to use this drywall calculator
- Choose Whole room and enter the length, width and wall height, or choose Individual walls for one wall, a partition or an odd-shaped room.
- Tick Include the ceiling if you are boarding it too.
- Enter doors and windows you want to leave out. Typical sizes are filled in, and you can change them.
- Pick the sheet size you plan to buy and keep about 10–15% extra for cuts and mistakes.
- Read the sheet count, plus rough quantities of screws, tape and joint compound for your shopping list.
Drywall calculation formula
Board area = Wall area [+ Ceiling area (Length × Width)]
Sheets = Board area × (1 + Waste %) ÷ Sheet area (round up)
Worked example: a 12 × 14 ft room with ceiling
- Walls: 2 × (12 + 14) × 8 = 416 sq ft, minus 1 door and 2 windows (≈ 50.6 sq ft) = 365.4 sq ft
- Ceiling: 12 × 14 = 168 sq ft, so the board area is 533.4 sq ft
- With 10% waste: 586.7 sq ft ÷ 32 sq ft per 4 × 8 sheet = 18.3, so buy 19 sheets (or 13 sheets of 4 × 12)
- Rough finishing materials: about 590 screws, 200 ft of tape and 5 gallons of joint compound (two 4.5-gal boxes)
In metric: a 4 × 3.5 m room with 2.4 m walls, one door, one window and the ceiling needs about 46.7 m² of board. With 10% waste that is 18 sheets of 1200 × 2400 mm, about 57 m of tape and roughly 18 litres of joint compound.
Drywall sheet sizes
| Sheet | Area | Common use |
|---|---|---|
| 4 × 8 ft | 32 sq ft (2.97 m²) | Easiest to carry and hang on your own |
| 4 × 10 ft | 40 sq ft (3.72 m²) | Taller walls, fewer joints |
| 4 × 12 ft | 48 sq ft (4.46 m²) | Long walls and ceilings, fewest joints |
| 1200 × 2400 mm | 2.88 m² (31 sq ft) | Standard metric plasterboard sheet |
| 1200 × 2700 mm | 3.24 m² (34.9 sq ft) | Rooms with taller ceilings |
Sheets needed for common rooms
Walls and ceiling, 8 ft (2.44 m) walls, no openings subtracted, 10% waste.
| Room | Board area | 4 × 8 sheets | 4 × 12 sheets |
|---|---|---|---|
| 10 × 10 ft | 420 sq ft | 15 | 10 |
| 10 × 12 ft | 472 sq ft | 17 | 11 |
| 12 × 12 ft | 528 sq ft | 19 | 13 |
| 12 × 14 ft | 584 sq ft | 21 | 14 |
| 14 × 16 ft | 704 sq ft | 25 | 17 |
| 16 × 20 ft | 896 sq ft | 31 | 21 |
Finishing materials: rules of thumb
The calculator’s screw, tape and compound figures are approximate planning numbers based on common estimating rules. Your real use depends on framing spacing, finish level and how carefully the joints are planned.
| Material | Rule of thumb |
|---|---|
| Screws (walls) | ≈ 1 per sq ft (≈ 32 per 4 × 8 sheet) |
| Screws (ceilings) | ≈ 1.33 per sq ft (≈ 42 per 4 × 8 sheet) |
| Joint tape | ≈ 370 ft per 1,000 sq ft (≈ 1.2 m per m²) |
| Joint compound | ≈ one 4.5-gal box per 475 sq ft (≈ 0.39 L per m²) |
Always follow the board manufacturer’s fastening schedule and local building codes. Ceilings, fire-rated walls and wet areas such as bathrooms often need specific board types and thicknesses.
Tips for planning your drywall
- Hang the ceiling first, then the walls, so the wall sheets help support the ceiling edges.
- Use the longest sheets you can handle. Fewer butt joints means less taping and a flatter finish.
- Hang wall sheets horizontally on most walls. It often reduces the total length of joints.
- Stagger joints so they don’t line up from row to row or fall at the edge of a door or window.
- Check the framing. Sheet edges should land on studs or joists. Mark stud positions on the floor and ceiling before you start.
- Order a sheet or two extra. A cracked corner or a mis-measured cut-out is common, and a spare saves a trip.
Planning to paint afterwards? New drywall needs a coat of primer first. Use our paint calculator to work out primer and paint for the same room.
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
A 12 × 12 ft room with 8 ft walls has 384 sq ft of wall plus a 144 sq ft ceiling, 528 sq ft in total. With 10% extra for waste that is 19 sheets of 4 × 8 ft drywall, or 13 sheets of 4 × 12 ft. Subtracting doors and large windows lowers the count slightly.
How many screws do I need per sheet of drywall?
As a rule of thumb, about 1 screw per square foot on walls (around 32 per 4 × 8 sheet with framing at 16 in centres) and about 1.33 per square foot on ceilings (around 42 per 4 × 8 sheet). Follow the board manufacturer’s and local code fastening schedule.
How much joint compound do I need?
A common planning figure is one 4.5-gallon box of pre-mixed all-purpose compound for roughly 475 sq ft of drywall, covering taping and two finish coats. A higher finish level, such as a full skim coat, needs noticeably more.
How much joint tape do I need?
Plan for roughly 370 linear feet of tape per 1,000 sq ft of drywall (about 1.2 m per m²). Rooms with lots of corners and short pieces use more.
Should I subtract doors and windows for drywall?
Subtract doors and large windows. Many installers don’t subtract small windows, because the cut-out piece usually ends up as waste anyway. If in doubt, leave openings out and keep the 10–15% waste allowance.
Should I use 4x8 or 4x12 sheets?
Longer sheets mean fewer joints to tape and a smoother finish, so 4 × 12 sheets are popular for walls and ceilings. They are heavier and harder to carry through doors and stairs, so you may need a helper or a drywall lift. 4 × 8 sheets are easier to handle on your own.
What size is metric plasterboard?
In the UK, Europe and Australia the most common sheet is 1200 × 2400 mm, with 1200 × 2700 mm and other lengths also available. Check what your local supplier stocks before you plan the layout.
Last reviewed November 5, 2026.