Block quantity calculator
Estimate how many concrete blocks you need for a wall from its area, so you order the right quantity of blockwork.
Result
Blocks required
How to use this calculator
- Measure the wall area (length × height, minus large openings).
- Enter the area below.
- Read the number of blocks to order.
Assumptions
- Standard 440 × 215mm block size with 10mm mortar joints.
- Area already excludes large openings such as doors and windows.
Technical details: what the fields mean
- Wall area
wallAreaM2 - Total wall area, in square metres.
- Waste allowance
wastePercent - Extra blocks to cover breakages and cut blocks at corners/openings.
Methodology
Blocks = area × 10 × (1 + waste%). 10 blocks/m² assumes a standard 440 × 215mm concrete block with 10mm mortar joints — the standard figure UK builders' merchants use.
Worked example
15m² block wall, 5% waste
Inputs: wallAreaM2=15, wastePercent=5
Result: 158 blocks required
Practical guidance
- Blockwork is usually faster to lay than brick — factor that into labour-cost comparisons.
- Check whether your design needs standard, dense or lightweight (thermal) blocks; density affects cost, not quantity.
Common mistakes
- Applying the 10/m² figure to a non-standard block size.
- Forgetting to subtract large openings from the area.
FAQs
How many concrete blocks do I need per square metre?
About 10, for a standard 440 × 215mm block with 10mm mortar joints.
Does block size affect the quantity needed?
Yes — this calculator assumes the standard 440 × 215mm block. A different size needs a different blocks-per-m² figure.