Formula
Each brick takes up its length plus one joint, by its height plus one joint, on the face of the wall. One divided by that area is bricks per square metre for one skin. A double skin doubles it.
Bricks are the net wall area, length times height minus openings, times bricks per square metre, times one plus waste, rounded up.
Mortar is the wall’s volume minus the bricks’ volume, plus waste. Dry mix is that times 1.33. Cement is the dry mix divided by one plus the sand parts, at 1440 kg/m³; sand is the rest at 1600 kg/m³.
Worked example
A 215 × 65 mm brick with 10 mm joints is 59.26 a square metre for one skin. 5 m by 1.2 m is 6.00 m², so 355.6 bricks net and 373.3 bricks, rounded up to 374 with 5% waste.
Mortar is 0.111 m³. At 1:5 that takes 35.4 kg of cement, 2 bags, and about 197 kg of sand.
Assumptions
Joints are 10 mm both ways. A double skin has a 10 mm joint between the two leaves and no cavity.
The mortar uses solid bricks. Frogs and perforations take more mortar than this, so treat the cement count as a floor.
Lime and plasticiser are not counted. A 1:5 or 1:6 cement and sand mix with plasticiser is a common general mortar; follow the mix your job is specified to.
Checked
Checked 11 November 2026. The Brick Development Association gives the UK work size as 215 × 102.5 × 65 mm with a 10 mm joint, and Travis Perkins quotes about 60 bricks a square metre. Austral and Midland Brick list 230 × 110 × 76 mm at 48.5 a square metre. B&Q lists Blue Circle cement at 25 kg; Bunnings lists general purpose cement at 20 kg. The 1.33 dry-volume factor and the cement and sand densities are assumptions.