Estimate bricks or blocks for a rectangular wall using the actual unit size and mortar joints. Deduct openings, choose an ordering allowance and enter your premixed mortar yield to estimate bags.
Divide 1 by (brick length + joint) × (brick height + joint), with dimensions in metres. A 215 × 65 mm brick with 10 mm joints gives 59.26 units/m² per skin, commonly rounded to about 60. This is an area estimate; end joints, bond, corners, cuts and special bricks need a separate take-off.
With no openings, 215 × 65 × 102.5 mm bricks and 10 mm joints, one skin has 12 m² of face area and an estimated 711.11 bricks. A 5% breakage allowance gives 747 bricks to order. The geometric joint volume is 0.2114 m³; adding 15% gives 0.2431 m³. If your selected premixed mortar yields 12 litres per bag, that is 21 bags. The 12-litre yield is an example, not a default for all products.
Skins must use the same unit dimensions. For an outer brick skin and an inner block skin, calculate each separately. Collar joint thickness defaults to zero: enter only a deliberately mortar-filled joint between adjacent skins. Never enter an empty or insulated cavity as a mortar joint.
This geometry assumes rectangular units and full-width bed and vertical joints. It excludes frogs, perforation filling, hollow-block face-shell bedding, grout and edge effects. Enter an allowance appropriate to your product and method. For hollow blocks or specialist systems, use the manufacturer’s mortar consumption figures.
No mortar mix is prescribed. For premixed mortar, enter the mixed-volume yield in litres per bag from the selected product data sheet. Zero leaves the bag count unset. Sand and cement cannot be reliably inferred from wet joint volume alone: mix specification, moisture and batch yield matter. See the Ibstock technical resources for brickwork guidance and confirm your mortar product specification.
Wall and unit lengths follow the mm/inch selector. Opening area stays in square metres, and bag yield stays in litres. The drawing is a capped schematic of the gross wall; it does not locate openings or provide a laying plan.
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