Drywall Calculator
Everything a plasterboard job buys, from one area figure: sheets, CD/CW profiles, screws, joint tape, putty — and hangers when it is a ceiling. Consumption per square metre follows the Knauf tables, waste is applied before rounding, and rounding happens once, into whole sheets.
A system, not a sheet
Plasterboard sells as a system: board, profile, fastener, tape, putty — and the consumption figures per square metre are published by the manufacturers because every element scales off the same area. The whole estimate is that one area pushed through five multipliers.
The one figure worth double-checking on site is the area itself: openings under about a square metre are conventionally not subtracted, because their cutouts become the offcuts the rest of the job needs.
Frequently asked questions
Why does a ceiling need more profile than a wall?
Geometry of the frame: a wall carries vertical CW studs at 600 mm spacing, a ceiling hangs a CD grid at 500 mm with cross-connections — about 2.9 metres of profile per square metre against a wall's 2. The hangers line appears for ceilings only, because walls stand on the floor.
When is a double layer worth it?
For sound insulation, fire rating, or walls that will carry shelves: the second layer doubles mass and stiffens joints because seams are staggered. It doubles sheets and screws but not the frame — the calculator reflects exactly that split.
Seventeen screws per square metre — why so many?
Spacing at 250 mm along every stud a sheet crosses works out near 17/m² for single layer. Fewer and the board drums; the count is also why buying screws by the small box is a mistake — a 20 m² wall wants three hundred and forty of them.
Does the putty here cover the whole surface?
No — this is joint putty: seams, screw heads and corner beads, about 0.45 kg/m². A full skim coat before painting is a separate product and a separate calculation; the plaster calculator next door handles surface coats by thickness.
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