Why use this calculator
Bricks are ordered in packs and delivered on a truck with a crane, so being short by a hundred units means a second delivery charge that can exceed the value of the bricks themselves, and being short of a discontinued or specially blended brick can mean a visible colour difference across a wall forever.
The count per square metre is the number everyone quotes and almost nobody checks against the brick they are actually buying, yet it varies from roughly 48 to 75 per square metre between countries because the face sizes genuinely differ. This calculator uses the real face dimensions and joint thickness rather than a single rule of thumb, and shows the same wall priced in every common unit so a substitution can be assessed immediately.
How to use it
- Choose the brick or block you are actually buying, because the count per square metre depends on it and the differences between countries are large.
- Enter the total run of walling, adding separate walls together, and the finished height from the damp proof course or slab up to the top course.
- Add up every door and window by multiplying each opening's width by its height and enter the combined area to deduct.
- Say whether the wall is a single leaf or a cavity wall with two separate skins, since a cavity wall needs twice the bricks, and finally set a wastage allowance, using around five per cent for plain walls and ten or more where there are many cuts.
What each result means
- Bricks or blocks to order
- The quantity to actually buy, including wastage. Round up to whole packs, since most suppliers will not split a pack.
- Units before wastage
- The theoretical count for the net area. Never order this figure, because cuts and breakages are unavoidable.
- Units per square metre
- How many units cover a square metre of wall face, derived from the real face size plus the joint rather than a generic rule of thumb.
- Net wall area
- Wall area after deducting doors and windows. Deducting openings is what separates a realistic order from an expensive over-order.
- Total face area laid
- The area actually bricked. A cavity wall doubles this because each skin is laid separately.
- Mortar volume
- Approximate wet mortar needed to bed and perpend every unit. Mixing a test batch before ordering in bulk is worth the hour.
- Cement needed
- Bags of cement for a 1:4 mix by volume. Buy a little extra, since part-used bags absorb moisture and go off quickly.
- Sand needed
- Bricklaying sand by weight. Order sharp or bricklaying sand specifically, not the fine sand sold for rendering.
- Courses in the wall height
- How many courses fit the height. A fraction means the top course will need cutting or the height adjusting to a whole course.
The formula
Units per square metre = 1 divided by ((face length plus joint) multiplied by (face height plus joint)) in metres
Net wall area = length multiplied by height, minus the area of openings
Total face area = net area multiplied by the number of leaves
Units required = face area multiplied by units per square metre, then multiplied by 1 plus the wastage percentage
Mortar volume is derived from the joint volume surrounding each unit multiplied by the bed depth and the number of units, and sand and cement follow from a 1:4 mix by volume at roughly 320 kg of cement per cubic metre.
How this number is used in practice
Designing to whole courses saves both money and appearance. A brick course is the unit height plus the joint, so an Australian brick runs at 86 mm and a UK brick at 75 mm. Setting window heads, sills and the top of a wall to land on a course line avoids cutting an entire row of bricks lengthwise, which is slow, wasteful and visibly worse.
Bricklayers call this working to gauge, and adjusting a wall height by twenty or thirty millimetres at design stage to achieve it is almost always worth doing.
Mortar estimates are the least reliable part of any masonry take-off, because the actual quantity depends on joint thickness, how full the perpends are laid, the absorbency of the brick and how much is dropped. The figure here is a reasonable planning number, but the practical approach is to mix a small batch, lay a square metre and count what it took.
Ordering sand by the tonne bag is cheap; running out mid-wall on a hot day when the mortar is going off is not.
Buy the whole job in one delivery where you can. Bricks are fired in batches and colour varies measurably between them, so a top-up delivery weeks later can be visibly different in a wall already built. Suppliers call the matching batch a blend, and once it is gone it is gone.
This is why experienced bricklayers order generously, keep the surplus for future repairs, and mix bricks from several packs as they lay rather than working through one pack at a time.
Worked examples
A 10 m by 2.4 m single-leaf wall in Australian standard bricks with 4 m2 of openings
969 bricks before wastage and 1,037 to order with 7 per cent added
The same wall built as a cavity wall with two skins
The count doubles to 1,938 before wastage, which is 2,074 to order
The same wall in 390 x 190 mm concrete blocks instead
Only 250 blocks, because each block covers more than four times the face area of a brick
When people use it
- Ordering bricks or blocks for a wall, extension or garden project
- Checking a builder's quantity take-off against your own before signing off
- Comparing the unit count when substituting a different brick size
- Estimating sand and cement so a mortar order arrives with the bricks
- Working out whether a wall height lands on a whole course before construction
Tips
- Order the whole job at once. Bricks vary in colour between firing batches, so a top-up delivery can be visibly different.
- Design wall heights to whole courses. An Australian brick course is 86 mm and a UK course 75 mm including the joint.
- Mix bricks from several packs as you lay. It blends any colour variation instead of banding it across the wall.
- Deduct openings honestly but keep the wastage allowance. Bricks around an opening need cutting and the offcuts are rarely reusable.
- Keep a pallet of spares for future repairs. Matching a discontinued brick years later is close to impossible.
- Order bricklaying or sharp sand, not the fine sand sold for rendering. The wrong sand gives a weak, crumbly joint.
What it assumes, and where it stops being accurate
- Assumes a 10 mm joint for metric bricks and 9.5 mm for US units. Working to a different joint thickness changes the count per square metre.
- Mortar quantities are indicative only. Actual use varies widely with joint fullness, brick absorbency and how much is wasted.
- Assumes stretcher bond, the common single-brick-thick pattern. Decorative bonds such as Flemish use more units per square metre.
- Deducts openings at their full area, which slightly under-orders because bricks around an opening need cutting. The wastage allowance is meant to absorb that.
- Excludes lintels, wall ties, damp proof course, insulation and any reinforcement, all of which are priced separately.
- Assumes a uniform wall. Piers, returns and corners need extra units that a simple area calculation does not capture.
Terms used on this page
- Course
- One horizontal row of bricks, measured as the unit height plus the joint.
- Perpend
- The vertical mortar joint between bricks in the same course.
- Stretcher bond
- The common pattern with each brick laid lengthwise and offset half a brick from the row below.
- Leaf or skin
- One thickness of masonry; a cavity wall has two separated by an air gap.
- Gauge
- The bricklayer's set-out of course heights, used to make openings and wall tops land on a joint.
Questions people ask
- How many bricks are in a square metre?
- It depends on the brick. An Australian standard brick with a 230 by 76 mm face and a 10 mm joint gives about 48.4 per square metre, a UK brick about 59.3, and a US modular brick about 74. Concrete blocks are far fewer, around 12.5 per square metre.
- Should I deduct windows and doors?
- Yes, deduct their full area, but keep a wastage allowance because bricks around openings have to be cut and the offcuts are usually unusable. Leaving openings in the calculation can over-order by hundreds of bricks on a wall with several windows.
- How much wastage should I allow?
- Around five per cent for a plain wall with few cuts, and ten per cent or more where there are many openings, corners, piers or decorative details. Cutting a brick to fit generates one unusable offcut, so wastage tracks the number of cuts rather than the wall area.
- What is the difference between single leaf and cavity?
- A single leaf is one brick thick. A cavity wall is two separate skins with a gap between for insulation and drainage, so it needs twice the bricks plus wall ties. Most modern external walls are cavity construction in the UK and Australia.
- How much mortar will I need?
- Roughly one cubic metre per 1,000 standard bricks, though this varies considerably with joint thickness and how fully the perpends are filled. Mix a test batch and lay a square metre to get a reliable figure before ordering sand and cement in bulk.
- Does bond pattern change the count?
- Yes. Stretcher bond, the usual single-skin pattern, is what this assumes. Decorative bonds such as Flemish or English include headers laid across the wall, which increases the number of units per square metre of visible face.
Use this with
Brick and Block Calculator answers one part of the question. These pick up where it stops: Concrete Volume Calculator, Roof Pitch and Rafter Calculator, Stair Rise and Run Calculator and Fencing Materials Calculator.
Where these figures come from
This calculation is jurisdiction-neutral arithmetic. No country-specific rules are applied.
- Think Brick Australia. Australian brick dimensions, bonds and masonry technical guidance
- Brick Development Association. UK brick sizes, bonds and mortar specification
- Brick Industry Association. US modular brick dimensions and technical notes on masonry
Brick and Block Calculator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.