Brick Calculator

Brick counts are usually quoted as a rate per square metre or per square foot of wall face, and the rate depends on how thick the wall is. A half-brick wall showing one face of each brick needs roughly half as many bricks per square metre as a full one-brick wall built from two leaves. This calculator works from the wall's actual dimensions and thickness, and lets you set the brick size so it matches what your supplier is actually delivering.

Because bricks always come with mortar, the mortar volume is calculated too, along with the cement and sand needed to mix it. That matters because the cement for mortar is frequently forgotten at ordering time and then bought in a rush at a higher price.

Why we count by wall face, not by volume

A common shortcut is to divide the wall's volume by the volume of one brick. It is quick and it is wrong for most walls, because a wall is built from whole leaves of brickwork and its thickness is never an exact multiple of a single brick plus its joint. A 230 mm wall built from 115 mm bricks is two leaves with a collar joint between them — the volume method treats that collar as part of the bricks and comes out roughly 9% low.

Counting by face area avoids the problem entirely. Each leaf of brickwork shows one brick face per module, so the rate per square metre is simply the reciprocal of the module area, multiplied by the number of leaves. It is the method estimators use, and it is why a 230 mm wall comes out at about 100 bricks per square metre while a 115 mm wall comes out at about 50.

Standard, modular and imperial bricks

Brick sizes are not universal, and using the wrong one throws the count off by a large margin. The two you will meet most often:

• Standard 230 × 115 × 75 mm (about 9 × 4½ × 3 in) — the traditional brick across South Asia, the Middle East and much of Africa. At a 10 mm joint it gives roughly 50 bricks per m² as a half-brick wall, or 100 per m² at one brick thick.
• Modular 190 × 90 × 90 mm — the metric brick used in Europe, Australia and North America, designed so that four bricks plus joints make exactly 800 mm. At a 10 mm joint it gives 50 bricks per m² for a 90 mm wall, and 100 per m² for a 190 mm wall.

US bricks follow a different convention again — the nominal dimensions include the mortar joint, so a “2¼ × 4 × 8 inch” brick is really 2¼ × 3⅝ × 7⅝ with a ⅜ inch joint. If your supplier quotes nominal sizes, the joint is already baked in; select the closest option and check the per-square-metre rate the calculator shows against the supplier's own figure before ordering.

Worked example

A garden wall 10 metres long and 3 metres high in 230 mm brickwork. The wall face is 30 square metres. With 230 × 115 × 75 mm bricks at a 10 mm joint, the calculator returns 99 bricks per square metre, which is 2,942 bricks — about 3,090 once the 5% breakage allowance is added.

The same 30 square metres at 115 mm thick is a single leaf and needs 1,471 bricks, almost exactly half. That difference is the whole point of checking the wall thickness before ordering: guessing wrong on a garden wall is a four-figure mistake in any currency.

The mortar for the 230 mm wall works out at about 1.02 cubic metres wet, or 1.36 cubic metres of dry mix — roughly 7 bags of 50 kg cement and 1.13 cubic metres of sand at a 1 : 5 mix.

How much waste to allow

Allow 5% for machine-made bricks delivered on pallets and handled carefully. Allow 8–10% where bricks are hand-made, where they are unloaded and carried across a site by hand, or where the wall has many openings, corners and returns that generate cut bricks.

Keep the surplus. Brick colour and texture vary between kiln batches, and a wall repaired two years later from a different batch will show the join. A few hundred spare bricks stored dry and covered will save a great deal of trouble, and they cost almost nothing relative to the wall.

Mortar mix and joint thickness

A 1 : 5 cement-to-sand mix is the general-purpose choice for most brickwork. Go to 1 : 4 for load-bearing walls and anything exposed to driving rain, because the extra cement improves both strength and weather resistance. Drop to 1 : 6 only for internal non-load-bearing partitions, where strength is not the issue and a softer, more workable mix is easier to lay.

Keep the joint at about 10 mm. Thicker joints use more mortar and are weaker; thinner joints leave less room for the brick's own dimensional variation, which matters more with hand-made bricks. Consistency across the wall matters as much as the nominal figure — a wall with joints varying between 8 and 15 mm is both weaker and visibly uneven.