About this calculator
Count concrete (Besser) blocks for garden walls, foundation walls, garages and extensions, along with the mortar to lay them.
How it’s calculated
A standard 390 × 190 block (20.01 series) with 10 mm joints covers 400 × 200 mm, which works out to 12.5 blocks per m². Blocks = net wall area × blocks per unit area, plus waste.
Worked example
With these inputs:
- Wall length
- 10 m
- Wall height
- 2.4 m
- Openings area
- 0 m²
- Block
- 390 × 190 × 190 mm (20.01)
- Mortar mix
- 1:1:6 cement:lime:sand (M3, general)
- Waste allowance
- 5%
the result is:
- Blocks needed
- 315 blocks
- Wall area (net)
- 24 m²
- Courses
- 12
- Mortar volume (wet)
- 0.64 m³
- Mix 1:1:6 needs
- 8 × 20 kg cement + 3 × 20 kg lime + 0.7 m³ brickies sand
Tips from the trade
- Subtract openings, but add back for lintel bearings and cut blocks at the ends.
- Order a few extra half-blocks or cutters for corners and ends.
- Core-filled and reinforced walls need block-fill concrete and steel on top of this. Work the core fill out with the wall calculator.
Common questions
How many blocks per square metre?
12.5 standard 390 × 190 blocks per m² with 10 mm joints.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.