What this calculator does
Brick count depends on the unit size plus the mortar joint, not the unit alone. A standard 230 by 76 mm brick with a 10 mm joint occupies 240 by 86 mm of wall, giving 48.4 bricks per square metre.
Ignoring the joint is the common error and it is a large one. Without the 10 mm joint the same wall would need 57.2 bricks per square metre rather than 48.4, an 18% overestimate. The mortar occupies real space, and over a wall of any size that difference is hundreds of bricks.
The formula
Each unit occupies its own dimensions plus one joint thickness in each direction, so the effective area per unit is length plus joint multiplied by height plus joint. The wall area divided by that gives the count, with the waste allowance added on top. The figure covers a single-leaf wall; a double-leaf cavity wall needs twice as many.
| Term | Meaning |
|---|---|
| Unit | A brick or block. Standard metric brick is 230 × 76 mm in Australia, 215 × 65 mm in the UK. |
| Mortar joint | Typically 10 mm. It counts toward the space each unit occupies. |
| Single leaf | One unit thick. A cavity wall has two leaves and needs double the count. |
| Waste allowance | For breakages and cuts. 5% is usual for brickwork. |
The inputs explained
| Field | What to enter |
|---|---|
| Wall length (m) | Wall length in metres. |
| Wall height (m) | Wall height in metres. |
| Unit length (mm) | Unit length in millimetres. |
| Unit height (mm) | Unit height in millimetres. |
| Mortar joint thickness (mm) | Mortar joint thickness. 10 mm is standard. Setting it to zero gives a dry-stacked count. |
| Waste allowance (%) | Waste allowance for breakages and cuts. |
When to use it
Ordering bricks for a wall
Bricks come by the pack, and the count determines how many packs.
Comparing brick and block
Blocks cover far more area per unit, so a block wall goes up much faster.
Estimating a garden wall
A straightforward single-leaf wall is exactly what this calculation suits.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does the joint change the count?
The same wall at a range of mortar joint thicknesses.
| Mortar joint | Units needed | Units per m² | Wall area |
|---|---|---|---|
| 0 mm | 962 | 57.2 | 16.00 m² |
| 5 mm | 883 | 52.5 | 16.00 m² |
| 10 mm | 814 | 48.4 | 16.00 m² |
Questions
How many bricks per square metre?
About 48 for a 230 by 76 mm brick with a 10 mm joint, or about 59 for the smaller 215 by 65 mm UK standard. For a double-leaf cavity wall, double whichever figure applies, since each leaf is counted separately.
Does the mortar joint really matter?
Substantially. At 10 mm the joint adds about 4% to the length and 13% to the height of each unit, and mortar ends up occupying roughly 15% of the wall face. Omitting it from an estimate overshoots the brick count by a similar margin.
How much waste should I allow?
5% covers ordinary breakage and cuts on a simple wall. Increase it for walls with many openings, angles or feature courses, where more bricks are cut and fewer offcuts are reusable.
Does this account for a cavity wall?
No, it calculates a single leaf. A standard cavity wall has two leaves, so double the result. If the leaves use different units, run the calculation twice with the respective sizes rather than doubling one figure.
For mortar quantities, see the mortar calculator. For retaining wall blocks, see the retaining wall block calculator.