Counting bricks, cement and sand for a wall
How to work out the bricks, cement and sand for a wall, the difference between modular and conventional bricks, half-brick and full-brick walls, mortar mixes and how much wastage to allow.
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In short
- Bricks = wall area ÷ ((brick length + joint) × (brick height + joint)) × leaves. A half-brick wall has one leaf and a full-brick wall has two.
- A 230 × 75 mm brick with a 10 mm joint gives 49 bricks a square metre on each leaf, so a 20 × 10 ft nine-inch wall takes about 1,822 bricks.
- Mortar is the part of the wall that is not brick, about a fifth of it. Multiply that wet volume by 1.33 for dry material, then split it by the mix.
- Allow about 5 percent extra on bricks, and take doors and windows off the area first.
- One cubic metre holds about 500 modular bricks but only about 408 conventional ones, so always quote the size with the count.
The count of bricks is the first number a house builder asks for, and it is the one most often guessed. Masons quote "so many bricks per square foot", which is fine when the wall is ordinary and the brick is the one they know. It goes wrong when the brick size changes, when the wall is half-brick rather than full, or when no one has taken the door off the area. This page sets out the arithmetic the calculator uses, so you can check a contractor's figure before you order a truck.
The formula
Bricks are easiest to count from the face of the wall. One brick, with the mortar around it, covers a rectangle slightly larger than the brick itself:
bricks per leaf = wall area ÷ ((brick length + joint) × (brick height + joint))
A leaf is one layer of bricks seen from the side. A half-brick wall, about 4.5 inches thick, is one leaf. A full-brick wall, about 9 inches thick, is two leaves side by side with a joint between them.
bricks = bricks per leaf × number of leaves
Take a wall 20 ft long and 10 ft high. That is 200 sq ft, or 18.58 m². With a conventional 230 × 110 × 75 mm brick and a 10 mm joint, one brick and its joint covers 240 × 85 mm, which is 0.0204 m². So each leaf takes 18.58 ÷ 0.0204 = 911 bricks, and a nine-inch wall takes twice that, 1,822 bricks. With 5 percent wastage, buy 1,913.
Counting from the wall's volume, as many quick guides do, works for a thick wall but undercounts a half-brick one. The thickness of a half-brick wall has no joint inside it, so dividing its volume by a brick plus joint in all three directions gives too low a number. Counting from the face avoids that.
Which brick do you have?
Brick sizes in India are not uniform, and the difference matters more than it looks. The modular brick of the Indian standard is 190 × 90 × 90 mm, but a great deal of local kiln brick is nearer 230 × 110 × 75 mm. Fly ash and AAC blocks are different again.
| Brick | With a 10 mm joint | Per m², one leaf | 100 sq ft, half-brick | 100 sq ft, full-brick |
|---|---|---|---|---|
| Modular 190 × 90 × 90 mm | 200 × 100 mm | 50 | 465 | 929 |
| Conventional 230 × 110 × 75 mm | 240 × 85 mm | 49 | 455 | 911 |
The two look almost the same per square metre, because the taller modular brick makes up for its shorter length. Where they part is by volume. A modular brick with its joints takes up 0.002 m³, so a cubic metre of wall holds about 500. A conventional brick takes up 0.00245 m³, so a cubic metre holds about 408. When someone quotes "500 bricks a cubic metre", they mean the modular size, and it is the wrong number for a conventional brick.
Before relying on any count, measure a brick from the batch you will buy. Bricks from small kilns vary from one load to the next, and a few millimetres on each brick changes a large order.
Cement and sand for the mortar
Mortar fills whatever the bricks do not. Work out the wall's volume, subtract the volume of the bricks, and what remains is wet mortar:
wet mortar = wall volume − (bricks × volume of one brick)
For the 20 × 10 ft nine-inch wall, the volume is 4.27 m³ and 0.82 m³ of it is mortar, a little under a fifth. Sand and cement shrink when mixed with water, as the grains settle together, so the dry material needed is larger than the wet volume. The usual site factor is 1.33:
dry mortar = wet mortar × 1.33
That dry volume is then shared out by the mix. In a 1:6 mix, one part in seven is cement and six in seven is sand. A 50 kg bag of cement is 0.0347 m³, because cement weighs about 1,440 kg/m³.
| Mortar mix | Used for | Cement, 20 × 10 ft 9-in wall | Sand |
|---|---|---|---|
| 1:6 | Ordinary inner walls | 4.47 bags | 32.9 cu ft |
| 1:4 | Outer or loaded walls | 6.26 bags | 30.7 cu ft |
Which mix to use is a decision for the engineer or the mason's experience with the local sand, not for a calculator. A leaner mix saves cement but gives a weaker wall.
Half-brick and full-brick
A half-brick wall uses half the bricks but well under half the mortar, because it has no joint running down the middle. The same 20 × 10 ft wall built half-brick takes 911 bricks, 957 with wastage, along with 1.73 bags of cement and 12.7 cu ft of sand at 1:6.
Half-brick walls are the norm for partitions inside a framed building, where the concrete columns and beams carry the load. Full-brick walls are used for outer walls and for load-bearing construction. If you are not sure which your drawing calls for, ask, because the two differ by a factor of two in bricks.
Taking off doors and windows
Enter the area of the openings and the calculator subtracts it. On the same wall, one door and one window totalling 40 sq ft bring the area down to 160 sq ft, and the count from 1,822 to 1,457 bricks. Skipping this on a whole house can over-order by a noticeable margin.
Masons sometimes ignore small openings, reasoning that the cuts around them waste as many bricks as the opening saves. That is fair for a small ventilator, but not for a door.
How much wastage?
Some bricks break in the truck and in stacking, and others are cut at corners and openings. About 5 percent is usual with good bricks and simple walls, rising to 10 percent with weak bricks, many openings or a long unloading distance. Soak-and-sort losses from poorly burnt bricks can be higher, so look at a sample before you order the whole load.
Buy a little over rather than a little under. A top-up load later may come from a different batch, and the delivery of a few hundred bricks costs nearly as much as a full truck.
Costing the wall
Enter the prices of a brick, a bag of cement and a cubic foot of sand, and the calculator gives a material cost. That figure is materials only. Labour is usually quoted per square foot or per thousand bricks, and it can be a large share of the bill. Remember too that a brick wall needs plaster on both sides, which is a separate quantity. For the concrete parts of the job, use the cement calculator, and for the reinforcement, the steel weight calculator.
What this calculator assumes
- All bricks are one size, and joints are the same thickness in both directions.
- A half-brick wall is one leaf and a full-brick wall is two leaves with a joint between them.
- Wet mortar becomes dry material by a factor of 1.33, and a 50 kg bag of cement is 0.0347 m³.
- Bricks that are cut at corners and openings are covered by the wastage figure, not counted separately.
- The result is an estimate for ordering. It is not a structural design, and an engineer should decide wall thickness and mix for any load-bearing work.