About this calculator
How much cement and plaster sand a wall needs for internal or external plaster, with common or masonry cement.
How it’s calculated
Quantities per 100 m² at 15 mm come from the Concrete Society of Southern Africa’s mix leaflet (SANS 2001-EM1): internal plaster with common cement takes 600 kg of cement and 2.3 m³ of plaster sand (two bags to six wheelbarrows); external plaster takes 700 kg and 2.25 m³ (two bags to five wheelbarrows). With masonry cement (MC 22,5X or MC 12,5), internal plaster takes 700 kg and external 850 kg, each with 2.25 m³ of sand. Other thicknesses are scaled from 15 mm.
Worked example
With these inputs:
- Wall length
- 4 m
- Wall height
- 2.4 m
- Openings to subtract
- 0 m²
- System
- Internal plaster, common cement
- Plaster thickness
- 15 mm
- Waste allowance
- 10%
the result is:
- Materials needed
- 2 × Cement, 50 kg bag + 0.5 m³ Plaster sand (by the cube)
- Area (incl. waste)
- 10.56 m²
- System
- Internal plaster, common cement
Tips from the trade
- Uneven or chased walls take more plaster. Add 10–20%.
- Dampen very absorbent brickwork before plastering, so it doesn’t draw the water out of the plaster too fast.
Common questions
How much cement do I need to plaster 100 m²?
Per 100 m² at 15 mm with common cement: 600 kg (12 bags) for internal plaster and 700 kg (14 bags) for external plaster, each with about 2.25 to 2.3 m³ of plaster sand.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.