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Drywall & Plasterboard Calculator
Sign up to favourite this calculatorFind how many sheets of drywall or plasterboard a room needs from its length, width and height, with doors, windows and waste allowed for. Switch between UK metric boards and US imperial panels.
Plasterboard sheets to buy
2400 × 1200 mm (8 × 4 ft) plasterboardGross area
50.00 m²Doors and windows
3.50 m²Area to board
46.50 m²Estimated cost
46.50 m² of walls and ceiling plus 10.0% waste is 51.15 m². Divided by 2.88 m² per sheet that is 17.76, rounded up to 18 sheets.
Estimate only. Check the board type, thickness and sheet sizes your supplier stocks before ordering, and follow the manufacturer’s guidance for fire, moisture and sound ratings.
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Assumptions and limits
- An estimate from the numbers you entered, for guidance only. It is not financial, tax or medical advice.
- Calculator version 1, last updated 25 October 2026.
- Sources: USG: Sheetrock Wallboard Estimator, Gypsum Association: GA-216 Application and Finishing, Jewson: British Gypsum plasterboard guide.
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How to use this calculator
- Choose Metric for metres and UK plasterboard sizes, or Imperial for feet and US drywall panels. Switching converts the room size you have typed.
- Choose whether you are boarding the walls, the ceiling or both, then enter the room length, width and wall height.
- Enter how many doors and windows to leave out of the walls.
- Pick the sheet size you will buy and set the wastage allowance, 10% by default.
- Optionally choose a currency and enter the price of one sheet to see the total cost.
- Read the number of sheets to buy, with the area and the working shown underneath so you can check it.
What do I need to enter?
- Measurement system — Metric (metres, UK boards) or Imperial (feet, US panels).
- What are you boarding? — Walls and ceiling, Walls only or Ceiling only. Wall height, doors and windows are not used for a ceiling.
- Room length and Room width — above zero, up to 500 m or 1,500 ft.
- Wall height — above zero, up to 50 m or 150 ft.
- Doors and Windows — whole numbers from 0 to 99. Each door removes 2 m² (20 ft²) and each window 1.5 m² (15 ft²) from the walls.
- Sheet size — the board you will buy. UK offers 2400 × 1200, 1800 × 900, 2700 × 1200 and 3000 × 1200 mm; US offers 4 × 8, 4 × 10 and 4 × 12 ft.
- Wastage allowance — extra board for cuts and breakages, 0% to 50%.
- Currency and Price per sheet — optional. A price from 0 to 100,000 adds a total cost; leave it blank to skip the cost.
What do the results show?
- Plasterboard sheets to buy (drywall in imperial) — the whole number of sheets, rounded up, with the sheet size beneath it.
- Gross area and Doors and windows — the area before and the area removed for openings. Both appear only when you enter a door or window.
- Area to board — the net area after openings, before waste is added.
- Estimated cost — sheets × price per sheet, shown only when you enter a price.
- Working — the sum in words, so you can check the sheet count by hand.
How many sheets of drywall or plasterboard do I need?
The calculator finds the area to cover, takes off the openings, adds the waste allowance and divides by the area of one sheet, always rounding up to a whole sheet.
sheets = ⌈ net area × (1 + waste ÷ 100) ÷ sheet area ⌉
- wall area = 2 × (length + width) × height
- ceiling area = length × width
- openings = (doors × 2 m²) + (windows × 1.5 m²), or 20 ft² and 15 ft² in imperial
- net area = wall area + ceiling area − openings
The sum runs in the unit system you chose, against a sheet area in the same system. A UK 2400 × 1200 mm sheet is exactly 2.88 m² and a US 4 × 8 ft panel is exactly 32 ft²; neither is a converted figure. The two sheet lists are separate because the two markets sell different sizes.
Example, UK: a 4 m × 3.5 m room with 2.4 m walls, one door and one window
- Walls: 2 × (4 + 3.5) × 2.4 = 36 m². Ceiling: 4 × 3.5 = 14 m². Together 50 m².
- Openings: 2 + 1.5 = 3.5 m², leaving 46.5 m².
- With 10% waste: 46.5 × 1.1 = 51.15 m².
- 51.15 ÷ 2.88 = 17.76, which rounds up to 18 sheets of 2400 × 1200 mm.
Example, US: a 12 ft × 12 ft room with 8 ft walls, one door and one window
- Walls: 2 × (12 + 12) × 8 = 384 ft². Ceiling: 12 × 12 = 144 ft². Together 528 ft².
- Openings: 20 + 15 = 35 ft², leaving 493 ft².
- With 10% waste: 493 × 1.1 = 542.3 ft².
- 542.3 ÷ 32 = 16.95, which rounds up to 17 sheets of 4 × 8 ft drywall.
What size is a sheet of plasterboard or drywall?
UK boards are sold in millimetres and US panels in feet. The sizes below are the ones this calculator offers; larger and smaller sizes exist, and the J T Atkinson plasterboard range shows what a UK merchant stocks.
| UK sheet | Covers | Typically used for |
|---|---|---|
| 2400 × 1200 mm (8 × 4 ft) | 2.88 m² | The standard full sheet for walls and ceilings |
| 1800 × 900 mm (6 × 3 ft) | 1.62 m² | Easier to carry up stairs and through tight halls |
| 2700 × 1200 mm | 3.24 m² | Taller walls with fewer horizontal joints |
| 3000 × 1200 mm | 3.60 m² | Tall walls and long ceiling runs |
| US panel | Covers | Typically used for |
|---|---|---|
| 4 × 8 ft | 32 ft² | The standard panel for 8 ft walls and most home centres |
| 4 × 10 ft | 40 ft² | Taller walls and fewer seams |
| 4 × 12 ft | 48 ft² | Long walls and ceilings, fewer seams to finish |
The Gypsum Association lists US panels as 48 or 54 inches wide and 8, 9, 10, 12, 14 or 16 ft long. The calculator covers the three most common lengths; for a 54 inch panel, divide your area by the panel’s own area.
Which thickness and type of board do I need?
The board type and thickness decide how a wall performs, not how many sheets it takes, so they are not inputs. As a guide:
- UK thickness: 9.5 mm, 12.5 mm and 15 mm. 12.5 mm is the common choice for walls and ceilings.
- UK types: standard, moisture resistant for bathrooms and kitchens, fire resistant, acoustic and thermal laminate boards, as set out in Jewson’s British Gypsum guide.
- US thickness: 1/2 inch is common for walls, and 5/8 inch where more fire resistance or a stiffer ceiling is wanted.
- US types: regular, mould and moisture resistant, and Type X, the 5/8 inch fire-rated panel.
Fixing spacing is closer on ceilings than on walls. The Gypsum Association’s GA-216 standard sets the US rules, and the manufacturer’s installation guide covers the UK ones. For a wider US material estimate, USG publishes the Sheetrock Wallboard Estimator, which also counts joint compound, tape and fasteners but, like this tool, leaves out the waste allowance unless you add it.
What should I work out after the boards?
Once the walls are boarded and skimmed, the Paint Coverage Calculator estimates the paint for the finished room in litres or US gallons.
What does this calculator not do?
- It counts boards only. Screws, joint tape, jointing compound and corner bead are not included.
- It does not choose a board. Fire, moisture and sound ratings depend on the room and the manufacturer’s system, and do not change the sheet count.
- It removes a flat allowance for each door and window rather than their real sizes, so a very large opening is better handled by lowering the room height or raising the waste.
- It treats the room as a rectangle and assumes one sheet size for the whole job. It does not plan the layout or reuse offcuts, so an L-shaped room needs each rectangle worked out separately.
- It is an estimate, not a quote. Check quantities with your supplier before ordering.
Sources
- Gypsum Association: panel sizes and thicknesses. US panel widths, lengths and thicknesses.
- Gypsum Association: GA-216 Application and Finishing. Closer fastener spacing on ceilings than on walls.
- USG: Sheetrock Wallboard Estimator. US panel sizes, and the accessories this calculator leaves out.
- Jewson: British Gypsum plasterboard guide. UK board types and thicknesses.
- J T Atkinson: Plasterboard and sheets. UK sheet sizes sold by merchants.
The door and window allowances and the 10% waste default are typical trade figures, not official ones. This is general information, not a quote or professional advice.
Frequently asked questions
How many sheets of plasterboard do I need for a room?
Add the wall area (2 × (length + width) × height) to the ceiling area (length × width), subtract the doors and windows, add a waste allowance, divide by the area of one sheet and round up. A 4 m × 3.5 m room with 2.4 m walls, one door and one window needs 18 sheets of 2400 × 1200 mm board with 10% waste.
How many sheets of drywall do I need for a 12×12 room?
With 8 ft walls, a 12 ft × 12 ft room has 384 ft² of wall and 144 ft² of ceiling. After one door and one window and a 10% allowance, it needs 17 sheets of 4 × 8 ft drywall. Without doors, windows or waste it is 528 ft² ÷ 32 = 16.5, so 17 sheets.
What size is a sheet of plasterboard or drywall?
The standard UK plasterboard sheet is 2400 × 1200 mm (8 × 4 ft), which covers 2.88 m². Other UK sizes include 1800 × 900 mm, 2700 × 1200 mm and 3000 × 1200 mm. US drywall is 4 ft wide in 8, 10, 12, 14 and 16 ft lengths, so a 4 × 8 ft panel covers 32 ft². The US also sells 54 inch wide panels.
How much waste should I allow when boarding a room?
Ten per cent is the usual allowance for an average room and is the default here. A plain rectangular room can manage with about 5%. Allow 15% or more for lots of corners, bay windows, sloping ceilings or awkward cuts. Change the Wastage allowance box to suit your job.
Does the calculator subtract doors and windows?
Yes. It takes 2 m² off for each door and 1.5 m² for each window in metric mode, and 20 ft² and 15 ft² in imperial mode. These are typical sizes, not exact ones. Offcuts from openings are often reused, so a modest deduction plus the waste allowance is more realistic than removing every opening exactly.
What thickness of plasterboard or drywall should I use?
UK standard boards come in 9.5 mm, 12.5 mm and 15 mm; 12.5 mm is the usual choice for walls and ceilings. In the US, regular drywall is commonly 1/2 inch, and 5/8 inch is used where more fire resistance or a stiffer ceiling is wanted. Thickness does not change how many sheets you need, so the calculator does not ask for it.
Which board is right for a bathroom, kitchen or fire-rated wall?
In the UK, moisture-resistant plasterboard suits bathrooms and kitchens, fire-resistant board such as Gyproc FireLine is used where higher fire performance is needed, and acoustic board reduces sound travelling between rooms. In the US, mould and moisture resistant panels serve damp rooms and Type X, which is 5/8 inch, is the fire-rated panel. The sheet count is the same; check the manufacturer for the right board.
Does this calculator include screws, tape and joint compound?
No. It counts boards only. Fixings, joint tape and jointing compound depend on the framing spacing, the finish and the products you choose, so check the manufacturer’s coverage figures when you order them.
Should I use the same sheet size for walls and ceilings?
You can, and the calculator assumes one size for the whole job. Longer sheets mean fewer joints to finish, but they are heavier and harder to handle alone, so many people use shorter boards for ceilings and tight spaces.
How much does a sheet of plasterboard or drywall cost?
Prices vary by board type, thickness, supplier and region, so this calculator does not guess one. Enter the price of one sheet from your merchant or store and it multiplies by the number of sheets to buy. Pick your currency from the Currency list first.
Last updated 25 October 2026. Sources: USG: Sheetrock Wallboard Estimator, Gypsum Association: GA-216 Application and Finishing, Jewson: British Gypsum plasterboard guide.