Plaster Calculator

Because it multiplies everything: 25 m² at 10 mm of gypsum is 225 kg, at 20 mm it is 450. Walls are never even, so measure the gap to a straightedge at five or six points and use the average — one thick corner can add a bag by itself.

Gypsum for dry interior rooms: lighter per millimetre (≈0.9 vs ≈1.7 kg), smoother, faster. Cement for bathrooms, facades and anywhere damp — it tolerates water, weighs nearly double per layer, and the tonnage difference is exactly what the material presets show.

Ten per cent covers mixing losses, the bit that dries in the bucket and droppage. Machine application wastes less, first-timers more. The waste is applied to the kilograms before rounding, so it never buys a phantom bag on its own.

No — primer is a liquid with its own per-m² figure and its own calculator logic (litres, not bags). This page counts the plaster body only; budget primer separately at roughly 0.1–0.2 L/m² per application.