Brick & Mortar Calculator

Work out how many bricks, how much mortar, cement and sand a wall needs. Handles four wall thicknesses, three brick sizes, openings and a wastage allowance.

Brick counts are easy to get wrong because the joint, the wall thickness and the openings all change the answer. Enter the wall, pick the brick and the joint, and the page returns bricks with waste, wet mortar, cement bags and sand. The per-square-metre table below is recalculated with your brick and joint settings.

The wall

Measure the clear length and height of the wall, then subtract the openings. Wall thickness is the finished thickness including the joint.

Wall length (m) Wall height (m) Wall thickness Brick size (mm) Mortar joint (mm) Openings to deduct (m²) Wastage allowance (%) Cement : sand (by volume)

Bricks to buy –

Net wall area –

Wet mortar –

Cement –

Sand –

Cement bags (50 kg) –

How this was worked out

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Materials per square metre of finished wall

Wall	Bricks	Mortar	Cement

Four rules before you order

Order bricks in whole packs and add 5–10% waste. Breakage on site is normal, and a second delivery costs more than the spare bricks.
The joint is part of the count. Going from a 10 mm to a 12 mm joint cuts roughly 5% of the bricks and adds mortar, so decide the joint before you order.
Deduct every opening larger than about 0.5 m². Small holes for pipes and sockets are usually left in the count.
Cement bags are 50 kg in most markets. Buy sand by the cubic metre or tonne and keep it covered; wet sand bulks up and throws off the mix.

Practical notes

A 240 mm wall is not two leaves of 115 mm with a gap — it is one brick length thick, so the face count is about half of what people guess.
For a first course or a pier, count the bricks by drawing the bond on paper. Bricks are cheap; cutting and redoing is not.
Mix only what you can lay in about 90 minutes. Mortar that has started to set must be thrown away, not re-tempered with water.

Three common mistakes

Multiplying the wall area by a remembered "bricks per square metre" figure without checking the wall thickness. The same area is four times the brick count at 490 mm compared with 115 mm.
Using the wet mortar volume as the dry material volume. Dry cement and sand pack down and shrink, so the dry mix is about 1.2 times the wet volume.
Forgetting the piers, lintels and return walls. Measure them as separate rectangles and add them to the total.