Brick Calculator

How the brick calculator works

A 20 × 6-ft single-wythe wall — 120 sq ft — takes 906 modular bricks and 16 bags of mortar mix. With a ⅜-inch joint, each modular brick plus its mortar covers 0.146 sq ft, which is 6.9 bricks per square foot, or 823 bricks before waste; a 10% waste factor brings that to 906. Build the same wall double-wythe and the brick count doubles to 1,811.

The formula: for each brick + its mortar joint, the area covered = (brick_length + joint) × (brick_height + joint). Wall area = length × height, divided by area-per-brick gives raw count. Multiply by 2 for double-wythe walls, then add a 10% waste factor for cuts, breakage, and pattern misalignments.

Standard brick sizes and what they cost you in count

Brick sizes are not arbitrary. Modular sizing exists so that three courses of brick plus their bed joints come to exactly 8 inches, which lets brickwork line up with block, window openings, and floor heights without cutting. The face dimensions — the length and height you see — are what drive your order, because the third dimension (depth into the wall) only matters for a double-wythe build.

The count difference between modular and king is more than 40% — 686 bricks against 480 for the same 100 square feet. That rarely translates into a 40% cost difference, because larger bricks cost more each, but it does translate directly into labour: fewer units and fewer joints is less time on the wall. If you are hiring the work out, ask whether the quote is per brick or per square foot before you assume a big brick saves you money.

Mortar joints change the count more than people expect

The calculator adds the joint to both dimensions before computing the face area, because every brick in a running bond effectively carries half a head joint at each end and half a bed joint top and bottom. A ⅜-inch joint is the industry standard and what the tool defaults to; ¼-inch and ½-inch are both in normal use.

Read that table in both directions. Going from ¼″ to ½″ joints drops your brick count by about 12% — and roughly doubles your mortar. Mortar is the cheaper material, so wider joints are usually a small net saving on materials, but they are also more mortar to mix, carry, place, and strike. The joint width is an aesthetic decision first; the cost effect is a consequence, not a reason.

Single-wythe vs double-wythe

A wythe is one continuous vertical thickness of masonry. Nearly every brick house built since the mid-twentieth century is single-wythe: the brick is a rain screen hung on the outside of a wood- or steel-framed structural wall, tied back with metal anchors, with a drainage cavity behind it. It carries its own weight and nothing else. A double-wythe wall is two thicknesses bonded together, and it is genuinely structural — the norm in pre-1940s construction and still used for freestanding garden walls, piers, and some commercial work.

Two cautions on double-wythe. First, the calculator doubles the brick count, which is correct for facing units, but a properly bonded double-wythe wall uses header courses — bricks turned sideways to span both wythes — every fifth or sixth course in common bond. Headers show a different face dimension, so a real header-bonded wall lands a few percent off the doubled figure. Second, any freestanding double-wythe wall over about 3 feet tall is a structural element with real foundation, reinforcement, and lateral-support requirements. Check your local code and, above roughly 4 feet, get an engineer or an experienced mason involved.

Mortar planning, and a widely repeated number that is wrong

Rule of thumb: about 58 modular bricks per 60-lb bag of pre-mixed mortar at ⅜-inch joints, or roughly 1.7 bags per 100 bricks. Larger bricks have proportionally more joint length per unit, so they take more mortar per brick: about 53 queen, 47 king, or 38 utility bricks per bag.

Be careful with the widely repeated "125 bricks per bag" figure. That describes a bag of masonry cement, which yields roughly a cubic foot of mortar once you add your own sand — not a 60-lb bag of pre-mixed mortar, which yields about 0.45 cubic feet. Applying the masonry-cement number to premix underbuys by roughly 2.5×, and it is the single most common reason people run out of mortar on a Saturday afternoon. This calculator derives mortar from joint geometry — bed joint plus head joint, across the brick's 3⅝-inch depth — rather than from a rule of thumb, which is why its bag counts run higher than the numbers you will find repeated elsewhere. One simplification to be aware of: the mortar estimate assumes a 3⅝-inch bed depth for every size, so for the shallower 3-inch queen and king units it runs modestly conservative. Erring high on mortar is the right direction to err — a spare bag keeps.

We use 60-lb (27 kg) bags as the unit; 80-lb (36 kg) bags exist and cost less per pound, but smaller bags are easier to manage on a scaffold. On mortar type: Type N is the general-purpose choice for residential veneer above grade — it is deliberately weaker than the brick, so cracks form in the joints where they can be repointed rather than through the units. Type S goes in load-bearing and below-grade work and anywhere with real lateral load. Type M is for foundations and retaining walls. Stronger is not better: a mortar harder than the brick transfers stress into the units and spalls their faces. The mortar calculator shows the full breakdown including sand and cement for site-mixed batches.

Worked example: a 30 × 4-ft queen-brick garden wall

Enter 30 ft length, 4 ft height, queen size, single-wythe, ⅜-inch joint, 10% waste. Each brick plus joint covers (8 + 0.375) × (2.75 + 0.375) = 8.375 × 3.125 = 26.17 sq in, which is 0.1817 sq ft — 5.5 bricks per square foot. The wall is 120 sq ft, so 120 ÷ 0.1817 = 660 bricks raw; ×1.10 gives 727 bricks. Mortar works out to 14 bags of 60-lb premix.

Worth noting what this example is not telling you. A freestanding 4-foot garden wall in queen brick is single-wythe only if it has piers or a return every few feet — a bare 4-inch-thick wall 30 feet long and 4 feet tall will not survive a good wind. In practice you would either build it double-wythe (1,453 bricks) or add piers at intervals, and either way it needs a footing below the frost line. The calculator sizes brick and mortar; it does not tell you the wall stands up.

Worked example: a 24 × 8-ft double-wythe wall in modular brick

Enter 24 ft × 8 ft, modular, double-wythe, ⅜-inch joint, 10% waste. Face area is 192 sq ft at 6.9 bricks per square foot, so 192 ÷ 0.1458 = 1,317 bricks per wythe raw; ×2 for the second wythe = 2,633; ×1.10 for waste = 2,897 bricks. Mortar comes to 22.5 cubic feet, or 51 bags of 60-lb premix.

At roughly 4.2 lb per modular brick that is about six tons of brick, plus a ton and a half of mortar mix — a delivery-and-pallet-jack problem before it is a masonry problem. It is also about 2,900 individual placements: at a competent bricklayer's pace of 300–500 face bricks a day, this is a week of skilled labour. If the number surprises you, that is the calculator doing its job — brick projects are almost always priced by count, and the count is almost always larger than the eye estimates.

Why 10% waste, and when to raise it

Ten percent covers breakage in transit and handling, the cuts at corners and openings, and the culls you will reject for colour or chipping. It is a floor, not a cushion. Raise it to 15% for walls with several window and door openings, any curved or angled work, herringbone or basketweave patterns, or a soldier-course band. Raise it further for reclaimed brick, where cull rates of 20–30% are normal. One more reason to round up generously: brick is a fired clay product and colour varies between production runs, so a second order weeks later may not match the first. Buy the whole job at once, from one run, and keep the leftovers for future repairs.

Frequently asked questions

Pair with the mortar calculator for a full mortar breakdown including site-mixed sand and cement.