Standard brick sizes
Last reviewed 1 July 2026
Short answer
The UK standard brick is 215 × 102.5 × 65 mm, giving a 225 × 75 mm co-ordinating size with 10 mm joints. US modular brick is 7⅝ × 3⅝ × 2¼ in, giving an 8 × 2⅝ in module with ⅜ in joints. The co-ordinating size is what determines coverage.
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Work size and co-ordinating size
The work size is the brick itself — what you measure with a tape. The co-ordinating size is the space it occupies in the wall, which is the work size plus one joint in each direction.
Everything about setting out uses the co-ordinating size. Four UK bricks plus their perpends span 900 mm exactly, which is why UK openings and pier spacings tend to work in multiples of 225 mm.
Three courses of UK brickwork rise 225 mm, which is the same as one block course. That is not a coincidence — it lets brick and block skins course together in a cavity wall.
UK sizes
| Unit | Work size (mm) | Co-ordinating size (mm) | Weight |
|---|---|---|---|
| Standard brick | 215 × 102.5 × 65 | 225 × 75 | 2.2–3.1 kg |
| Metric modular brick | 200 × 100 × 75 | 200 × 75 | About 2.6 kg |
| Concrete block, 100 mm | 440 × 215 × 100 | 450 × 225 | 16–20 kg dense |
| Concrete block, 140 mm | 440 × 215 × 140 | 450 × 225 | 22–28 kg dense |
| Aerated block, 100 mm | 440 × 215 × 100 | 450 × 225 | 8–10 kg |
Aerated blocks are roughly half the weight of dense aggregate blocks in the same size, which matters for a day of lifting.
US sizes
| Unit | Specified size (in) | Nominal size (in) | Per ft² |
|---|---|---|---|
| Modular brick | 7⅝ × 3⅝ × 2¼ | 8 × 4 × 2⅔ | 6.86 |
| Queen brick | 7⅝ × 3⅛ × 2¾ | — | 5.80 |
| Standard brick | 8 × 3¾ × 2¼ | — | 6.55 |
| Utility brick | 11⅝ × 3⅝ × 3⅝ | 12 × 4 × 4 | 3.00 |
| CMU, 8 in | 15⅝ × 7⅝ × 7⅝ | 16 × 8 × 8 | 1.125 |
US bricks are quoted by specified size; the nominal size includes the ⅜ in joint.
Why the joint width matters so much
Changing a UK joint from 10 mm to 12 mm changes the module from 225 × 75 mm to 227 × 77 mm, and coverage falls from 59.3 to 57.2 bricks per square metre.
That is a 3.5% swing from a 2 mm change nobody would notice by eye. It is the reason a wall built with generous joints runs out of bricks and a wall built tight has bricks left over.
It also affects coursing: over ten courses, a 2 mm difference in the bed joint is 20 mm of height, which is enough to put a wall out of level with an adjoining structure.
Note: Gauge rods exist for this reason
Safety notice: Material planning only