About this calculator
How much render a brick or block wall needs: site-mixed sand and cement, premixed bags, or thin-coat render on smooth blockwork.
How it’s calculated
Sand and cement render is worked out by volume at 15 mm, using a dry-volume factor of 1.3 and a 1:4 mix. A 20 kg bag of premixed render is taken to cover about 1.1 m² at 10 mm, and a 20 kg bag of thin-coat render about 4 m² at 3 mm. Check the bag for your product’s rate.
Worked example
With these inputs:
- Wall length
- 4 m
- Wall height
- 2.4 m
- Openings to subtract
- 0 m²
- System
- Sand & cement render 1:4, 15 mm
- Waste allowance
- 10%
the result is:
- Materials needed
- 3 × GP cement, 20 kg + 0.2 m³ Rendering (plasterers) sand, bulk
- Area (incl. waste)
- 10.56 m²
- System
- Sand & cement render 1:4, 15 mm
Tips from the trade
- Uneven or chased walls eat more undercoat. Add 10–20%.
- Check the suction of the background before choosing an undercoat.
Common questions
How much does a bag of render cover?
A 20 kg bag of premixed render covers roughly 1–1.2 m² at 10 mm. Thin-coat renders go much further, often around 4 m² at 3 mm.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.