About this calculator
Count concrete blocks for yard walls, foundation walls, garages and extensions, along with the mortar to lay them.
How it’s calculated
Canadian concrete blocks are metric: a 390 × 190 mm face with 10 mm joints covers 400 × 200 mm, which works out to 12.5 blocks per m², or about 1.16 per sq ft. Blocks = net wall area × blocks per unit area, plus waste.
Worked example
With these inputs:
- Wall length
- 40 ft
- Wall height
- 6 ft
- Openings area
- 0 sq ft
- Block
- 20 cm (8"), 190 × 190 × 390 mm
- Blocks per 30 kg mortar bag
- 10
- Waste allowance
- 5%
the result is:
- Blocks needed
- 293 blocks
- Wall area (net)
- 240 sq ft
- Courses
- 10
- Mortar mix bags (30 kg)
- 30 bags @ 10 blocks/bag
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.
- Grout-filled cores and bond beams need extra concrete. Work those out with the wall calculator.
Common questions
How many blocks per square foot?
About 1.16 standard 390 × 190 mm blocks per sq ft, or 12.5 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 code adopted in your province before ordering.