Plaster Calculator
Work out how much plaster you need for a wall or ceiling.
Plaster required
78kg
- 25 kg bags
- 4 bags
- Volume
- 0.06 m³
Assumes finish plaster at about 1,300 kg per cubic metre.
v1.0 · Reviewed September 2026
How this is worked out
Volume is area × thickness, converted to weight at 1,300 kg per cubic metre and then to whole 25 kg bags.
Worked example
- Surface area 20 m²
- Thickness 3 mm
20 × 0.003 = 0.06 m³, and 0.06 × 1300 = 78 kg
78 kg, which is 4 × 25 kg bags
Assumptions and limits
- The 1,300 kg per cubic metre figure suits finish plaster. Bonding and browning coats are heavier and are usually applied thicker.
- Mixed plaster has a working life of well under an hour, so mix to what you can apply.