How many sheets of drywall do I need?

Divide the net area you are boarding (gross surface area minus doors and windows) by the area of one sheet, then add a wastage allowance and round up to whole sheets. A UK 1200x2400 mm sheet covers 2.88 m2; a US 4x8 ft sheet covers about 2.97 m2. This calculator does that for every wall and ceiling you list at once.

How much wastage should I add for drywall?

Ten percent is a sensible default for a simple room. Add more (15 to 20 percent) for rooms with lots of corners, sloped ceilings, small awkward spaces or an inexperienced installer, because off-cuts above doors and below windows rarely fit elsewhere.

How many screws per sheet of drywall?

A common trade rule is roughly 28 to 32 screws per sheet for walls fixed to studs at 16 inch or 400 mm centres, and a few more for ceilings. This tool uses about 30 per sheet as a balanced average; tighter ceiling fixing schedules or metal framing can need more.

How much joint compound and tape will I use?

As a rule of thumb you need about 0.5 kg of joint compound and 1.5 metres of joint tape per square metre of boarded area, covering taping, two filling coats and a skim. Textured finishes, level-5 finishes or wide bedding joints use more, so treat the figure as a starting estimate.

Does it work in feet and inches or only metric?

Both. Switch the units selector to imperial to enter every measurement in feet (decimals such as 2.4 ft are fine), and all areas, tape lengths and sheet sizes are shown back in feet and square feet. Sheet presets include US 4x8 and 4x12 as well as UK metric boards.

Is my data sent anywhere?

No. Every calculation runs in your browser using JavaScript. Nothing you type is uploaded, saved to a server or shared, so you can use it on private renovation budgets freely.

Drywall Calculator — Gera Tools

A drywall calculator that turns your room measurements into a precise shopping list: how many sheets of plasterboard, how many screws, how much joint compound and tape, and — if you add prices — the total material cost. It is built for DIY renovators, builders pricing a job and anyone boarding out a room, a garage, a loft conversion or a partition wall. List as many wall and ceiling surfaces as you like, deduct the doors and windows, and the tool does the area maths, the sheet packing and the consumables in one pass. Everything works in metric metres or imperial feet, and every number is calculated locally in your browser.

How it works

The calculator adds up the area of every surface you list — width times height times the number of identical surfaces — to get the gross area. It then subtracts the combined area of your doors and windows to get the net area you actually need to board. If you choose double boarding (two layers, common for soundproofing or fire upgrades), the net area is multiplied by the number of layers to get the boarded area.

To find the sheet count it uses an area-with-wastage method:

sheets = ceil( boarded area × (1 + wastage%) ÷ area of one sheet )

Rounding up to whole sheets reflects the fact that off-cuts rarely line up to be reused. Consumables then scale with the boarded area using standard trade rules of thumb: about 30 screws per sheet, 0.5 kg of joint compound per square metre, and 1.5 metres of joint tape per square metre. Each consumable is rounded up into whole boxes, bags and rolls based on the pack sizes you enter, and multiplied by the unit prices to give a costed breakdown.

Worked example

Say you are boarding a small bedroom: four walls each 4 m wide by 2.4 m high, with one 0.9 by 2.0 m door and one 1.2 by 1.2 m window to deduct, using UK 1200 x 2400 mm sheets and a 10% wastage allowance.

Gross wall area: 4 × (4 × 2.4) = 38.4 m2
Openings: (0.9 × 2.0) + (1.2 × 1.2) = 1.8 + 1.44 = 3.24 m2
Net area to board: 38.4 − 3.24 = 35.16 m2
Area per sheet: 1.2 × 2.4 = 2.88 m2
Sheets: ceil( 35.16 × 1.10 ÷ 2.88 ) = ceil( 13.43 ) = 14 sheets
Screws: 14 × 30 = 420 (≈ 3 boxes of 200)
Joint compound: 35.16 × 0.5 ≈ 17.6 kg (1 bag of 25 kg)
Joint tape: 35.16 × 1.5 ≈ 53 m (1 roll of 90 m)

At £9 a sheet that is £126 of board before screws, compound and tape — and the calculator totals all four lines for you.

Reference and formula note

Sheet coverage depends on the board you buy: UK 1200 x 2400 mm = 2.88 m2, UK 900 x 1800 mm = 1.62 m2, US 4 x 8 ft ≈ 2.97 m2, US 4 x 12 ft ≈ 4.46 m2. The consumable factors used here — roughly 30 screws, 0.5 kg of compound and 1.5 m of tape per square metre of board — are planning averages, not exact quantities. Ceiling fixing schedules, metal stud framing, level-5 finishes and textured coatings all push usage up, so treat the output as a buy-list estimate and confirm against your board manufacturer’s fixing guide. The tool deliberately rounds every purchasable item up to a whole unit and recommends keeping one spare sheet for repairs.