How to Use the Brick & Block Calculator
Measure the overall face of the wall — total length and total height, from footing or damp course to the top of the last course. Enter those two numbers and let the openings wait: for a quick estimate, a 5% waste factor absorbs a small window or two, but a door is 2 m² of a 20 m² wall, so subtract large openings from your wall dimensions instead of hoping waste covers them. Gables and stepped walls go in as separate calculations, one rectangle per step.
The count itself comes from the module, not the brick. A standard metric brick is 215 mm long and 65 mm high, but it gets laid with a 10 mm joint on every side, so the wall is really built from 225 × 75 mm modules. One module covers 0.016875 m², which inverts to 59.3 bricks per m² — the origin of the classic "60 per square metre" field figure for single-skin work. Every preset in this calculator works the same way:
| Unit | Work size | Module at 10 mm joint | Units per m² |
|---|---|---|---|
| Metric brick | 215 × 102.5 × 65 mm | 225 × 75 mm | ≈ 59.3 (the "60 per m²" figure) |
| US modular brick | 194 × 92 × 57 mm | 204 × 67 mm | ≈ 73 |
| UK block | 440 × 215 × 100 mm | 450 × 225 mm | ≈ 9.9 (about 10 per m²) |
| US CMU 8 × 8 × 16 | 406 × 203 × 203 mm | 416 × 213 mm | ≈ 11.3 (nominal sizing gives about 12) |
Skin matters as much as size. A single-skin (half-brick) wall is one wythe thick — about 102.5 mm for metric brick — and suits garden walls, bin stores and internal linings. A double-skin wall is two wythes, about 215 mm, and roughly doubles both the unit count and the mortar. Modern cavity walls are two thin skins tied together across a gap, so calculate each leaf separately and add wall ties to the materials list.
The mortar figure uses typical trade factors: about 0.026 m³ of mortar per m² of brickwork at a 10 mm joint, and about 0.012 m³ per m² of blockwork — blocks are bigger, so there is far less joint per square metre. Both scale with your joint thickness (half the joint, roughly half the mortar). For 1000 metric bricks, that works out to about 0.44 m³ of mortar; field rules of thumb run anywhere from 0.4 to 0.6 m³ depending on joint size and waste, so treat the row as a planning figure and take the detail to the mortar calculator.
Waste covers cuts, breakages and the half-bricks that end a bond pattern. Five percent is normal for a plain rectangular wall in running bond; use 8–10% once you add a gable, soldier courses or heavy cutting around openings. Bricks are ordered by count — sometimes by the pack — so round up to whatever your merchant actually sells.
For the full workflow — measuring complicated walls, mixing bond patterns, cavity details — read the brick wall quantity guide, and the mortar mix ratios guide for what to do with the mortar figure once you have it.