Free plasterboard calculator: enter your room length, width and height, choose whether you're boarding the ceiling, and instantly get the plasterboard sheets, jointing compound, scrim tape and screws needed to board and finish the job. Add your board, compound, tape and screw prices for a full material or installed cost estimate. Works in metric and imperial.
Openings (deducted from walls)
Common: 2.4 / 2.7 / 3.0 / 3.6 m long × 1.2 m wide (also 0.9 and 1.35 m wide).
Enter your prices - leave any blank to skip it. The board count comes from your rooms above; for the screws, compound and tape, set the pack you're buying and the calculator works out how many. Covers the board, screws, compound and tape only; corner bead, insulation, sanding and paint are extra.
Boarded area
45.60 m²
Screws
~576
Joint compound
~29.2 kg
Joint tape
~55.4 m
Got your numbers but want someone to do the work? Find trusted local handymen and tradespeople in the UK on ukhandyman.directory.
Drywall (plasterboard) is sold in sheets that clad the studs, then the joints between them are taped and filled. The calculator sizes both the boarding and the finishing from your room dimensions:
wall area = 2 × (length + width) × height - openings
ceiling = length × width (if you board it)
sheets = ceil( (wall area + ceiling) × wastage ÷ sheet area )
screws = sheets × 32
compound = boarded area × 0.64 kg/m²
tape = boarded area × 1.2 m/m²
By default the wall area treats the room as a closed box. Add the doors and windows on each room and the calculator subtracts their area from the walls - handy when a room has large openings that would otherwise have you buying boards you only cut to waste. Leave the openings off for a quick closed-box estimate where the wastage allowance covers the offcuts.
This example follows the unit system you pick in the calculator above.
A 4 × 3 m room, 2.4 m high, ceiling boarded, with 2.4 × 1.2 m sheets and 10% wastage:
| Item | Rule of thumb |
|---|---|
| Screws | ~32 per sheet (200-300 mm spacing); ceilings need more |
| Joint compound | ~0.6 kg/m² for a taped three-coat finish |
| Joint tape | ~1.2 m/m² of board |
| Corner bead | The length of each external corner, bought separately |
In the United Kingdom, plasterboard is typically sold as 1200 × 2400 mm and 900 × 1800 mm boards, usually 12.5 mm thick, fixed to studs at 400 or 600 mm centres and finished with jointing compound over the joints. Pick the board size you are actually buying in the calculator above so the sheet count matches what is on the shelf.
For the recognised installation and finishing detail - fastener spacing, joint treatment and the levels of finish - see British Gypsum's White Book installation guidance (to BS 8212 and BS EN 520).
Work out the area to board - the walls are the room perimeter times the ceiling height, plus the ceiling itself if you are boarding it - then divide by the area of one sheet and add wastage. A 4 × 3 m room 2.4 m high with the ceiling boarded comes to 45.6 m²; with 2.4 × 1.2 m boards and 10% wastage that is 18 boards. Enter your room and board size above for the exact figure.
Allow roughly 0.6 kg of jointing compound per square metre of board for a taped, three-coat finish - about a 28 kg box per 44 m². For tape, allow about 1.2 m per square metre. The calculator works both out from your boarded area.
Around 32 screws fix a standard 2.4 × 1.2 m board to studs at 400 mm centres - roughly a screw every 200-300 mm around the edges and down the centre studs. Ceilings are fixed more densely. The calculator multiplies your board count by 32 as a buy estimate.
If you are boarding a ceiling as well as the walls, tick "Board the ceiling" on each room and the calculator adds the floor area (length × width) to the boarded total. Board the ceiling first so the wall sheets tuck up under it and support the edges. Leave it unticked for a walls-only job.
Add each door and window to the room and the calculator deducts its area from the walls before working out the boards. Use the "+ Door" and "+ Window" buttons for a standard size, then edit the width, height and quantity to match. For a small room with one or two openings you can skip this and let the wastage allowance cover the offcuts; deduct them when the openings are large enough to save a board or two.
Add 10% for a simple room and 15% where there are lots of doors, windows, alcoves or services to cut around. Offcuts from openings can often be reused lower down or above doors, but it is safer to round up than to be one board short and stop the job.
Turn a room size or a square-footage figure into a drywall sheet count.
Read guide→Work out joint compound and tape from your boarded area, in boxes and rolls.
Read guide→Estimate drywall labor and material cost per square foot and per sheet.
Read guide→Studs, plate/track and plasterboard sheets for a partition wall, with cost built in.
Open calculator→Rolls, batts or blown-in bags - and cost - to hit a target R-value for walls, loft and ceilings.
Open calculator→Litres of paint for walls and ceilings, with coats and coverage built in.
Open calculator→How many tiles, boxes, adhesive and grout to buy for a floor or wall, with wastage and cost built in.
Open calculator→Linear metres of skirting board and how many stock lengths to buy.
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