Bricks and mortar for a wall

How it is calculated

Each laid brick, together with the mortar joint around it, takes up a rectangular "module" of (brick length + joint) × (brick height + joint). Bricks per m² is the inverse of that module's area: bricks/m² = 1 ÷ [(length + joint) × (height + joint)], with measurements in metres.

Net area = wall length × wall height − openings (doors, windows). Total bricks = net area × bricks/m² × (1 + waste allowance), rounded up.

Bonding mortar, by volume, is the difference between the wall's gross volume (net area × brick thickness) and the volume taken up by solid bricks in that same space. With hollow bricks the real mortar volume is somewhat higher than calculated, because mortar also partly fills the perforations of the first course of each layer and the chases; treat it as an approximate default quantity.

Example with the default values (brick 24×11.5 cm, thickness 9 cm, joint 1 cm): module = (0.24+0.01) × (0.115+0.01) = 0.25 × 0.125 = 0.03125 m² → 32 bricks/m². For a 5 × 2.5 m wall with a 1.5 m² opening: net area = 12.5 − 1.5 = 11 m². Bricks = 11 × 32 × 1.05 = 369.6 → 370 bricks. Mortar ≈ 11 × 0.09 × (1 − 0.24×0.115/0.03125) = 11 × 0.09 × 0.1168 = 0.116 m³.

Keep in mind

• Brick formats vary a lot by region and period; measure an actual brick before ordering material if you have access to one.
• The bonding mortar calculated here is only for the wall's joints, not the finishing render or plaster on its faces: for that use the mortar mix design tool with the area to cover and a typical thickness of 1.5-2 cm.
• For load-bearing walls or more than two storeys, the thickness and bonding pattern (brick arrangement) must be set by a structural calculation.