Ceiling Plasterboard (Gypsum Board) Sheet Calculator

Frequently asked questions

Does this apply to suspended (drop) ceilings?

No — this calculator is for gypsum board fastened directly to ceiling joists or furring channels. For a suspended grid ceiling with lay-in tiles, use the dedicated ceiling tile calculator instead.

Why do ceilings often need more waste allowance than walls?

Ceiling sheets are frequently cut around light fixtures, HVAC diffusers, sprinkler heads, and access panels, which produces more offcuts than a typical wall run — a 10% or higher allowance is common.

What sheet size should I enter if mine isn't 1.2×2.4m?

Enter the actual coverage area of one sheet (its width × its length) in whichever unit the field is showing. The field opens on a 1.2 m × 2.4 m sheet (2.88 m²) in metric and a 4 ft × 8 ft sheet (32 sq ft) in imperial.

Which way do the sheets run on a ceiling?

Across the joists or truss chords, long edges at right angles to them, so every sheet bridges several members and averages out their differences instead of following one of them. Stagger the end joints from row to row so they never line up across the room, and land each one on a joist or a nogging. Check the plane before the first sheet goes up: a joist standing 6 mm (1/4 in) proud is a shadow line that no amount of finishing will hide.

How close do the screws go on a ceiling?

Closer than on a wall, because the board hangs from them. Single-layer board is commonly screwed at 300 mm (12 in) centres on ceilings against 400 mm (16 in) on walls, at every framing member and round the perimeter. A fire-rated or acoustic system carries its own fixing schedule, and that schedule governs. Set each head to dimple the face paper without breaking it: a screw driven through the paper holds in the crumbling core alone, which is where first-year pops and a bellying ceiling come from.

How do I check this count against a sheet layout?

Draw the ceiling to scale with the sheets running across the joists. The number of rows is the room's dimension along the joists divided by the sheet width, rounded up; the sheets in each row are the other dimension divided by the sheet length, and the offcut that ends one row can start the next so the end joints stagger. Where the last row is a narrow ripped strip, the rest of those sheets is only useful if a strip of that width is wanted somewhere else. On a small ceiling that can put the layout a sheet above this count, which divides areas and cannot see where the rip falls; order the larger of the two.

What board sizes are sold for ceilings in the UK and in North America?

In the UK plasterboard is sold by the sheet, 1200 mm (about 4 ft) wide in lengths from 2400 mm (about 8 ft) upwards, and in smaller boards such as 900 × 1800 mm (about 3 × 6 ft) that one person can hold overhead. Tapered-edge board is made for taped and filled joints, and square-edge board is sold for ceilings that will be skimmed with plaster. In North America gypsum board, or drywall, is 4 ft (1.2 m) wide in 8, 10 and 12 ft (2.4, 3.0 and 3.7 m) lengths, with 54 in (1.37 m) widths and longer sheets from some suppliers. Enter the sheet you will actually buy: a 4 × 12 ft (about 1.2 × 3.7 m) sheet covers 48 sq ft (4.46 m²) and a 900 × 1800 mm board 1.62 m² (17.4 sq ft). A smaller board raises the count, and the number of joints to finish with it.

Does the count cover a second layer, or anything fixed with the board?

One layer only. A two-layer ceiling, built where a fire-resisting or acoustic system calls for one, needs this count twice, with the second layer's joints set off from the first so that no joint runs through both; the system's own details say which board goes in each layer. The figure is board alone. The screws are counted on the ceiling fastening page, and the resilient bars (resilient channel in North America) or furring, the insulation above, any vapour control layer (vapor retarder) and the tape and compound for the joints are all separate orders.

Should I enter rooms one at a time or add their ceilings together?

Each run rounds up to a whole sheet, so three rooms entered one at a time can come to as many as two sheets more than the same three areas entered together. The combined figure assumes an offcut from one room can finish another, which holds when the rooms are boarded in the same visit from the same stack, and not when one is boarded months later or on a floor the offcuts will never reach. Add together the ceilings that will share a delivery, and run the rest on their own.