A single-skin wall of standard UK bricks needs about 60 bricks per square metre, and a double-skin wall about 120. Multiply by the wall’s area, take off any doors and windows, then add 5–10% for waste. A 5 m × 1.8 m garden wall comes to 587 bricks to buy.
The 60 isn’t a rule of thumb pulled from nowhere. It comes from the size of a brick plus its mortar joint, and once you know that sum you can work out any wall, in metric or imperial.
How do you calculate how many bricks a wall needs?
Find the area of the wall, work out how much of it one brick covers, and divide. In four steps:
- Gross area is the wall’s length × height.
- Net area is the gross area minus the doors, windows and any other openings.
- Bricks required is the net area ÷ the face area of one brick including its mortar joints, doubled for a double-skin wall.
- Bricks to buy is the bricks required × (1 + waste), rounded up to a whole brick.
As a formula:
face = (length + joint) × (height + joint)
bricks = net area ÷ face × skins
bricks to buy = bricks × (1 + waste)Here face is the wall area one brick covers, joints included, and skins is 1 for a single skin or 2 for a double.
A worked example: a 5 m × 1.8 m garden wall
A standard UK brick measures 215 × 102.5 × 65 mm and is laid with a 10 mm mortar joint, which gives a co-ordinating size of 225 × 112.5 × 75 mm (Designing Buildings Wiki). Only the 215 mm length and the 65 mm height show on the face of a wall, so those are the two that count.
- Wall area. 5 × 1.8 = 9 m², with nothing to subtract.
- Area one brick covers. (0.215 + 0.010) × (0.065 + 0.010) = 0.225 × 0.075 = 0.016875 m².
- Bricks required. 9 ÷ 0.016875 = 533.3.
- Bricks to buy. With 10% waste, 533.3 × 1.10 = 586.7, rounded up to 587.
Run step 2 the other way and you get the headline figure: 1 ÷ 0.016875 = 59.3 bricks per square metre, which is the “about 60”.
Try it with your own wall
The calculator below opens with exactly this wall: 5 m by 1.8 m, single skin, standard UK brick, 10 mm joint and 10% waste. It shows 587 bricks, 533 before waste, and about 0.22 m³ of mortar. Change the length and height, add a door or window, or switch to concrete blocks, and the answer updates as you type.
9 m² ÷ 0.016875 m² per brick = 533.3 bricks, + 10% waste, rounded up = 587
Check the openings
Estimate only. Check your brick or block sizes and supplier guidance before ordering. For structural or retaining walls, get professional advice.
How do windows and doors change the count?
They come off the wall area before you divide, so a bigger opening means fewer bricks. Take the same 5 m run up to 2.4 m high and add one 1.2 m × 1.0 m window:
| Step | Result |
|---|---|
| Gross wall area (5 × 2.4) | 12 m² |
| Window (1.2 × 1.0) | −1.2 m² |
| Net area | 10.8 m² |
| Bricks required (10.8 ÷ 0.016875) | 640 |
| Bricks to buy (+10% waste) | 704 |
With no window the same wall needs 783 bricks, so the window saves 79. Add a standard 0.9 m × 2 m door as well and 3 m² comes off in total, leaving 9 m² of brickwork: the same 587 bricks as the garden wall.
Bricks around an opening have to be cut to fit, so don’t be tempted to drop the waste allowance on a wall with several openings.
Why do you have to include the mortar joint?
Because leaving it out is the most common way to over-order. Each brick sits in a bed of mortar and has a joint beside it, so it uses up a 225 × 75 mm patch of wall, not just its own 215 × 65 mm face.
| Method | Per m² | 9 m² wall, before waste |
|---|---|---|
| Brick face only (0.215 × 0.065) | 71.6 | 644 |
| Brick face plus 10 mm joints | 59.3 | 533 |
Dividing by the bare face overstates the count by about 21%. With 10% waste on top, that is 709 bricks instead of 587: 122 bricks you’d have paid for and carried for nothing.
How many bricks does a double-skin or cavity wall need?
Count each leaf of the wall separately. The gap between the leaves doesn’t change the brick count, so what matters is what each leaf is built from.
| Wall | Count per m² of wall face, before waste |
|---|---|
| Single skin (half-brick) of bricks | About 60 bricks |
| Double skin or solid one-brick wall | About 120 bricks |
| Cavity wall, brick outer and block inner | About 60 bricks and 10 blocks |
| Cavity wall, brick on both leaves | About 120 bricks |
For the 12 m² wall with the window, a double skin takes 1,408 bricks with 10% waste. A brick-and-block cavity wall takes 704 bricks for the outer leaf and 118 concrete blocks for the inner, each worked out with its own run of the calculator. Wall ties and cavity insulation are not counted, and their number and spacing come from the specification.
How many bricks, blocks or CMUs per square metre or foot?
A concrete block covers much more wall than a brick, so the count per square metre falls from about 60 to about 10. The US uses different units and a different brick, but the sum is identical: the working face of one unit, including its joint, divided into the wall area.
| Unit | Working face with joint | Count per unit area |
|---|---|---|
| UK brick, 215 × 65 mm face | 225 × 75 mm | 59.3 per m² |
| UK concrete block, 440 × 215 mm face | 450 × 225 mm | 9.9 per m² |
| US modular brick, 7 5/8 × 2 1/4 in | 8 × 2 5/8 in | 6.86 per ft² |
| US 8 × 8 × 16 in CMU | 8 × 16 in | 1.125 per ft² |
One UK block covers exactly the wall face of six bricks. On a fresh calculator, switching to Imperial loads a 16 ft × 6 ft wall of US modular brick: 96 ft² ÷ 0.145833 ft² per brick is 658.3, which is 725 bricks with 10% waste. Once you have typed your own measurements, the switch converts them instead.
How much waste should you allow?
Waste covers cut bricks, breakages in handling, and the odd brick with a chipped face you’d rather not put on show. There is no single correct figure, but these are sensible starting points, shown for the 9 m² wall:
| Waste allowance | When it suits | Bricks to buy |
|---|---|---|
| 0% | You have already added a margin of your own | 534 |
| 5% | A short, straight wall with few cuts | 560 |
| 10% | Openings, corners and a normal number of cuts | 587 |
| 15% | Complex openings or detailed brickwork | 614 |
Notice that 0% still gives 534, not 533: the calculator always rounds up to a whole brick. A few spares are also worth keeping, because a later order may not match the colour of the first.
How do you turn a brick count into an order?
Bricks are sold in packs, and the pack size varies from one range to the next, so ask your supplier for the figure for the brick you’ve chosen. Then divide your count by it and round up. If a range came in packs of 500, for example, the 704 bricks for the window wall is 1.41 packs, so you’d order two. Ask whether part packs are available before you commit to a pallet’s worth.
How much mortar will the wall use?
The calculator allows 0.022 m³ of mortar per square metre of single-skin brickwork (0.020 m³ for blockwork), doubles it for a double skin, then adds the same waste allowance. For the garden wall that is 9 × 0.022 × 1.10 = 0.2178, so 0.22 m³, or about 218 litres.
That is an allowance, not a measurement. How much mortar goes into a wall depends on the bricks, the bond and the bricklayer, and which mix to use depends on the brick and how exposed the wall is. Take the mix from the specification. The Brick Calculator page covers sand and cement in more detail.
What does a brick calculator not cover?
It counts materials and nothing else. It cannot tell you whether a wall is safe, whether it needs approval, or how deep its foundations should be.
If the wall needs a concrete footing first, the Concrete Volume Calculator works out how much to order for it.
What to do next
Open the Brick Calculator, enter your wall’s length and height, add its doors and windows, and pick a waste allowance. Divide the result by your supplier’s pack size, round up, and order it all in one go. For a US wall, switch to Imperial first and the defaults, labels and block sizes change with it.
Frequently asked questions
How many bricks do I need per square metre?
How many bricks do I need for a wall 5 m long and 1.8 m high?
How many extra bricks should I order for waste?
How many bricks do I need for a cavity wall?
How many bricks do I need per square foot in the US?
Sources: Designing Buildings Wiki: Brick sizes, Wienerberger UK: Choosing brick and mortar colour, and mixing packs, GOV.UK: Structure, Approved Document A.