How the brick calculator works
Every brick in a wall occupies its own face plus half of the mortar joint around it. So the number of bricks per square metre is one divided by the brick length plus one joint, times the brick height plus one joint. The net wall area (length × height minus openings) multiplied by that density gives the bricks for one skin, and a double skin doubles it.
Bricks = area ÷ ((L + j) × (H + j)) × skins × (1 + waste) · Mortar = (area × W × (1 − L × H ÷ ((L + j) × (H + j))) × skins + (skins − 1) × area × j) × 1.2Mortar is the part of the wall that is not brick: the same module volume minus the brick itself, across the full bed width W. For a double skin, the vertical collar joint between the two leaves (area × joint thickness) is added before the allowance: for a 10 m² wall of UK bricks with 10 mm joints built one brick thick, that brings the mortar from 0.423 to 0.543 m³. The 1.2 factor is a 20% allowance for mortar dropped from the trowel, cleaned off the face and left on the board. Dry mix is estimated at 1,900 kg per cubic metre of wet mortar (about 119 lb per ft³).
Worked example
A garden wall 5 m long and 2 m high, built as a single skin of UK standard bricks with 10 mm joints, has a 10 m² face. Each brick plus joint covers 0.225 × 0.075 = 0.016875 m², so the density is 59.26 bricks per m² and the wall needs 592.6 bricks, or 623 after a 5% allowance for breakage and cuts. The mortar share of each module is 17.2%, which over a 102.5 mm bed gives 0.0176 m³ per m², or 0.176 m³ for the wall. With the 20% allowance you mix about 0.211 m³, roughly 400 kg of dry mortar mix: 17 bags of 25 kg.
Common brick formats
| Format | Actual size | Bricks per m² | Bricks per ft² | Mortar per 1,000 bricks* |
|---|---|---|---|---|
| UK standard | 215 × 102.5 × 65 mm | 59.3 | 5.5 | 0.30 m³ |
| US modular | 7⅝ × 3⅝ × 2¼ in | 73.8 | 6.9 | 8.1 ft³ |
| US standard | 8 × 3⅝ × 2¼ in | 70.5 | 6.6 | 8.4 ft³ |
| German NF | 240 × 115 × 71 mm | 49.4 | 4.6 | 0.37 m³ |
*Solid bricks, 10 mm or 3/8 in joints, before the 20% allowance. Published US tables often quote 6.75 modular bricks per ft² because they use the nominal course height of 2⅔ in (three courses to 8 in).
Things that change the count
- Frogs and perforations. Bricks laid frog up, or cored bricks whose holes fill with mortar, can use a quarter to a half more mortar than solid units.
- Bond pattern. Stretcher bond in a single skin matches the calculation. Flemish or English bond in a one-brick wall uses the same number of bricks per m² of wall but more cutting at the ends.
- Piers and returns. Count each pier as extra wall area; a 5 m run with two piers easily needs 40 more bricks.
- Buy from one batch. Colour varies between firings, so order everything at once and draw from several packs as you lay.
- Height and loads. Freestanding garden walls above about 1 m, retaining walls and any load-bearing wall need a proper foundation and must follow local regulations; ask a structural professional.
Frequently asked questions
How many bricks are in a square metre?
About 60 UK standard bricks (59.3 exactly with 10 mm joints) make one square metre of single-skin wall, or about 119 for a double-skin, one-brick-thick wall.
How many bricks per square foot?
US modular bricks with 3/8 in joints come to 6.75 to 6.9 per ft², and US standard 8-inch bricks to about 6.6 per ft².
How much mortar do I need for 1,000 bricks?
Solid UK bricks with 10 mm joints need about 0.30 m³ of mortar per 1,000, or 0.36 m³ with a 20% allowance. Frogged bricks laid frog up need noticeably more.
How many bricks do I need for a 10 metre garden wall?
A 10 m wall that is 1 m high in single-skin UK bricks is 10 m², so about 593 bricks, or 623 with 5% waste. A one-brick-thick wall doubles that to around 1,245.
How much waste should I allow for bricks?
Allow 5% on straight walls with few cuts, and 10% where there are many corners, piers, openings or decorative bonds.
Last reviewed: 2026-09-27 · How we calculate