How many bricks do I need?

1. The formula, in plain English

Estimating brick is an area problem with one twist. Like tiling, you are covering a flat surface with fixed-size pieces, so the starting point is the wall area — its length times its height. The twist is the mortar joint. A brick does not occupy only its own face in the wall; it sits in a bed of mortar, so the repeating unit that actually tiles across the wall is the brick plus half a joint on every side. In other words, the space one brick claims is (brick length + joint) × (brick height + joint), and the number of bricks is the wall area divided by that unit area, rounded up.

This is exactly where the familiar rules of thumb come from, and why they are lower than the bare brick face would suggest. Take a US modular brick: its face is 7⅝ × 2¼ in, but with a ⅜ in mortar joint each brick occupies an 8 × 2⅝ in space — 21 square inches. A square foot is 144 square inches, so 144 ÷ 21 ≈ 6.86 bricks, which the trade rounds to “about 7 per square foot.” The same arithmetic in metric gives 60 bricks per square metre for a UK brick and around 50 for the larger Australian and New Zealand brick. The brick calculator does this for whatever brick size and joint you set.

2. A worked example

Suppose you are building a single-skin garden wall 10 ft long and 8 ft high. The area is 10 × 8 = 80 ft². At 6.86 modular bricks per square foot that is about 549 bricks before waste. Add a 10% allowance for cuts and breakage and you are ordering about 604 — call it 600-plus, and round to whole packs. If the same wall were one brick thick (a double skin), you would double the figure to roughly 1,100 bricks plus waste.

The metric version works identically. A wall 5 m long and 2.4 m high is 12 m². With a UK brick at about 60 per square metre that is about 712 bricks before waste, around 780 with 10% added. Build the same wall from the larger Australian brick at roughly 48 per square metre and it drops to about 582, or 640 with waste — a real difference of well over a hundred bricks on a small wall, which is why it pays to count in the brick you will actually lay rather than a generic number.

3. Standard brick sizes and bricks per area

Brick size is the biggest lever on your count, and it varies by country. Here are the common standards, with the single-skin bricks-per-area figure each gives once a normal mortar joint (⅜ in or 10 mm) is allowed for:

Notice how a bigger brick means fewer pieces: a wall takes far fewer Utility bricks than modular ones for the same area. Bigger bricks lay faster with less mortar, but each cut wastes more, so a job with lots of openings can justify a slightly higher waste percentage. Whatever brick you choose, these figures are for a half-brick (single-skin) wall — double them for a one-brick-thick wall, which is the other big lever on the total.

4. Single skin, double skin and openings

“Skin” (or wythe) is the thickness of the wall in bricks. A single skin is one brick thick — the half-brick wall used for a modern cavity wall's outer leaf, a brick veneer, or a low garden wall. A double skin is a solid one-brick wall, common for older buildings, taller freestanding walls and piers, and it simply needs twice the bricks per unit of face area. The calculator's wall-thickness selector switches between the two, which is the single most common reason a brick estimate comes out half what it should be.

Openings are the other adjustment. Doors, windows and air bricks remove brickwork, but the cuts around their edges create waste, so for a wall with only small or modest openings it is normal to measure the full rectangle and let the openings sit inside your waste margin. Only when an opening is genuinely large — a garage door, a wide window — is it worth subtracting its area before you apply the bricks-per-area figure. When in doubt, measure the full wall and round up; a spare pack is cheap insurance against a stalled job and a colour mismatch on the re-order.

5. What about the mortar?

The mortar joint is already built into the brick count — that is why the per-area figures are lower than the bare brick face implies. Estimating the bags of mortar mix is a separate question and depends on the joint thickness, the bond and the mix you use, so it is best taken from the bag's stated coverage rather than a single universal number. As a planning starting point only, many bricklayers reckon on roughly one bag of general-purpose mortar per 100–125 bricks for standard joints; treat that as a rough guide to confirm against your product, not a guarantee. If you are bedding the wall on a fresh footing, the concrete calculator works out the volume of that pour separately.

6. Buying bricks: batches, spares and ordering

Bricks are sold by the pack or pallet, and the colour can vary subtly between firing batches — the same trap as tile. Order the whole job, including the waste margin, in one delivery so the wall is laid from a consistent batch, and keep a few spares stored dry for future repairs. Round your total up to whole packs, because you cannot buy part of one, and check the brick size your supplier actually stocks against the figure you calculated, since “standard” covers a range of close-but-different sizes.

A brick estimate is one piece of a wall's budget. Tiling a wall in a wet area afterward? The tile calculator uses the same area method. Browse the other estimating tools on the masonry hub and across the site, estimate each material once with a sensible waste margin, and you will order close to right the first time — which is the whole point of working it out before the delivery turns up.

Common questions

How do you calculate how many bricks you need?

Measure the wall as length × height to get the area, divide by the area one brick takes up in the wall — its face plus a mortar joint — and round up, adding 5–10% for waste. For a standard US modular brick that works out to about 6.86 bricks per square foot (roughly 7); for a UK 215 mm brick it is about 60 per square metre; for an Australian or New Zealand 230 mm brick about 48 per square metre, all for a single-skin wall.

How many bricks do I need for a wall?

Take the wall area and multiply by the bricks-per-area figure for your brick, then add waste. A 10 × 8 ft single-skin wall is 80 ft², which is about 549 modular bricks before waste, or around 600 with a 10% allowance. A 5 × 2.4 m wall is 12 m² — about 712 UK-size bricks, or roughly 582 of the larger Australian size. A one-brick-thick (double-skin) wall needs twice as many.

How many bricks are there per square metre?

About 60 for a UK standard brick (215 × 65 mm face with a 10 mm joint) and about 48–50 for an Australian or New Zealand brick (230 × 76 mm), for a single skin. Those come straight from dividing one square metre by the brick-plus-joint area, and they double for a one-brick-thick wall.

How much extra should I order for waste?

About 5–10% for most brickwork. The allowance covers the bricks cut at openings, corners and returns plus the occasional broken or off-colour brick. Use the higher end if the wall has lots of openings or a feature bond, and keep a few spares from the same batch, because brick colour can shift between deliveries.