Ordering bricks by guesswork leads to either a half-finished wall or a pallet of leftovers you cannot return. The count depends on three things: the wall area, the size of your bricks, and the thickness of the mortar joints between them.
How it works
A standard brick with a 10 mm mortar joint covers about 0.019 square metres of wall face, which works out to roughly 50 to 60 bricks per square metre depending on the exact brick size and joint. For a single-skin wall, multiply wall area by bricks per square metre. For a double-skin wall, double it. Mortar volume is roughly the wall volume minus the brick volume, and in practice about one bag of cement per 100 to 150 bricks covers mortar for standard joints, with sand at roughly three to four times the cement volume.
Step by step
- Measure the wall length and height and multiply to get gross area.
- Subtract the area of doors, windows, and other openings.
- Find bricks per square metre for your brick size and joint, or use 60 per square metre as a planning figure for standard bricks with 10 mm joints.
- Multiply net area by bricks per square metre, then add 5 to 10 percent waste for cuts and breakages.
- Estimate mortar: allow about 0.03 cubic metres of wet mortar per square metre of single-skin wall as a planning figure.
- Round bricks up to the nearest pack size and order mortar materials to match.
Worked example
A single-skin wall 6 metres long and 2.4 metres high has a gross area of 14.4 square metres. Subtract a door of 2 square metres to get 12.4 square metres. At 60 bricks per square metre, that is 744 bricks. With 10 percent waste: 744 x 1.10 = 818.4, so order 820 bricks. Mortar planning volume is about 12.4 x 0.03 = 0.37 cubic metres of wet mortar.
Common mistakes
- Using gross area without subtracting openings, which over-orders on walls with large windows.
- Ignoring joint thickness. A 10 mm joint versus a 12 mm joint changes the count noticeably.
- Forgetting the second skin on a cavity wall and ordering half the bricks needed.
- Skipping the waste allowance, then running short on the last course.
Try it with the free tool
You can follow every step above by hand, but the free tool below does the same calculation instantly. Try your own numbers in it, then check one result by hand so you trust the method as well as the answer. Open the full tool here: open the tool.
Checklist before you finish
- Write down every input number first, with its unit, before you calculate anything.
- Work through the steps in order, and do not skip the unit conversions.
- Check the answer against the worked example above: is it the right size, and does the direction make sense?
- Round only at the end, and keep the unrounded figure for any follow-up calculation.
Practice with your own numbers
Pick three cases of your own and work each one by hand. First, try a simple round-number case you can check mentally. Second, try a realistic case with awkward numbers, the kind you will actually meet. Third, try an edge case, such as a very small or very large input, and confirm the answer still behaves sensibly. If any case gives a surprising result, re-check the units and the formula step by step before you trust it.
If your answer looks wrong
Most errors come from a small set of causes. Check that you used the same units throughout, that you divided where the formula divides and multiplied where it multiplies, and that you applied any percentage as a decimal. Check the order of operations: powers and brackets come before multiplication and division, which come before addition and subtraction. Finally, test the method on the worked example in this guide. If your method reproduces the example answer, the method is right and the inputs deserve a second look.
Quick tips
Confirm your brick size with the supplier before ordering, because brick sizes vary by region and maker. Keep a few spare bricks from the same batch for future repairs, since colour can vary between batches.