About this calculator
Count concrete blocks for garden walls, foundation walls, garages and extensions, along with the mortar to lay them.
How it’s calculated
A standard 440 × 215 block with 10 mm joints covers 450 × 225 mm, which works out to about 9.88 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
- 440 × 215 × 100 mm
- Mortar mix (cement:sand)
- 1:5 (general)
- Waste allowance
- 5%
the result is:
- Blocks needed
- 249 blocks
- Wall area (net)
- 24 m²
- Courses
- 11
- Mortar volume (wet)
- 0.3 m³
- Mix 1:5 needs
- 4 × 25 kg cement + 0.52 t building 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.
- Mortar figures assume normal 10 mm joints and include a practical allowance for droppings.
Common questions
How many blocks per square metre?
About 10 standard 440 × 215 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 Building Regulations before ordering.