Brick and Block Calculator
Count bricks or concrete block for a wall from its dimensions, net of openings, plus the mortar bags and masonry sand the job takes, priced at your rates.
Total run of wall in this unit type.
Face size including the mortar joint — that is what sets units per square foot.
Add up doors and windows and subtract them. A 3×7 door is 21 sq ft.
Single wythe, running bond, 3/8 inch joints. A double-wythe or cavity wall doubles the brick and changes the tie and flashing schedule entirely.
What this calculator does
It takes a wall length and height, subtracts the openings, and multiplies the remaining face area by the units-per-square-foot figure for the brick or block you are laying. Then it estimates mortar in 80-pound bags, masonry sand in tons if you are mixing rather than buying pre-blend, and prices the lot at whatever your supplier quoted.
Masonry estimating has one genuinely useful property: the units-per-square-foot figures are stable. They have not changed in decades, they are the same at every supplier, and once you know them you can estimate a wall in your head.
The numbers worth memorising
Modular brick — 6.75 per square foot. The standard US brick is 7-5/8 by 2-1/4 inches, laid with a 3/8-inch joint, which makes each unit occupy 8 by 2-2/3 inches of wall face. Divide 144 square inches by that and you get 6.75. Some estimators use 6.86 or round to 7; the difference across a whole house is a couple of hundred bricks, which is why waste allowance exists.
Queen brick — 5.75. Slightly taller face, fewer per square foot, and a common choice specifically because it lays faster.
Utility brick — 3.0. Much larger unit, and the reason it exists: a mason covers the same wall in less than half the placements.
Concrete block — 1.125. A nominal 8 by 16 face is 128 square inches, and 144 ÷ 128 = 1.125. In practice: 112.5 block per 100 square feet. This is the cleanest number in construction estimating.
Note that all of these are nominal dimensions — they include the mortar joint. That is exactly why they work: you never have to add anything for the mortar, because the mortar is already in the module.
Subtracting openings is not optional
A 40-foot wall at 8 feet high is 320 square feet, or 2,160 modular bricks. Put a door and three windows in it — say 40 square feet total — and the real number is 1,890. That is 270 bricks, and on a job where you are also paying to have them laid, it is not a rounding error.
Subtract full opening area. Do not try to be clever about the brick that gets cut around the perimeter of each opening — that is what the waste percentage is for, and openings are the single biggest source of waste on a brick job.
Mortar, and why block eats more of it
The estimating rules are old and reliable: about 7 bags per 1,000 brick, about 3 bags per 100 block.
Run those numbers per square foot and something looks backwards. A hundred square feet of brick is 675 units needing about 4.7 bags. A hundred square feet of block is 112 units needing about 3.4 bags. Block has one-sixth the joints and uses three-quarters the mortar.
The reason is joint volume. Brick joints are 3/8 inch on a 3-5/8-inch-deep unit. Block joints are 3/8 inch on an 8-inch-deep unit, and the head joints run the full 8 inches high. Fewer joints, but each one is far larger.
Weather moves these figures. Mortar has a working life measured in an hour or two, and in heat or wind a mason discards more of every batch. Budget generously in July.
Waste, and where it actually comes from
Ten percent is the default here, and unlike some trades that figure is not padding. Masonry waste is concrete:
- Cuts at openings and corners. Every window jamb is a column of cut brick.
- Breakage in transit and handling. Brick arrives on pallets and some of it arrives in pieces.
- Colour and blend culling. Brick is fired in batches and shade varies. A mason blending from three pallets to avoid banding will reject units.
- The pattern. Running bond wastes least. Anything with a soldier course, a rowlock sill or a header course wastes more.
Push toward 15 percent for a wall with many openings, and buy from a single production run if you can — matching brick a year later is close to impossible.
What this leaves out
- Second wythe. This counts one. A cavity wall is two, plus ties, flashing and weeps.
- Grout and core fill. Filled CMU cores are a large separate order — roughly 0.8 cubic feet per two cores at 8-inch block.
- Bond beams, lintels and reinforcement. Structural, drawn, and not estimated by face area.
- Foundation and footing. The concrete calculator covers what the wall stands on.
- Flashing, weeps, ties and expansion joints. All required, none counted.
- Scaffolding and labour. Usually the majority of the invoice.
For a garden wall rather than a structural one, the retaining wall calculator covers segmental block, base stone and the drainage that keeps it standing.
How this is calculated
net area = (length × height) − openings units = net area × units per square foot modular brick 6.75/sq ft · queen 5.75 · utility 3.0 · CMU 1.125 mortar: ≈ 7 bags per 1,000 brick · ≈ 3 bags per 100 block
Frequently asked questions
- How many bricks do I need per square foot?
- About 6.75 modular bricks per square foot of wall face, including the mortar joints. Queen size runs about 5.75 and utility brick about 3.0. Concrete block at the standard 8 by 16 nominal face works out to 1.125 per square foot, which is the easiest number in masonry — 112 block per 100 square feet.
- How much mortar does a brick wall need?
- Roughly 7 bags of 80-pound pre-blended mortar per 1,000 bricks, or about 3 bags per 100 concrete block. Block uses more per unit despite having fewer joints, because the joints are far wider. Cold, hot or windy weather all increase consumption because more mortar is discarded before it is used.
- Do I subtract windows and doors?
- Yes, and it matters more than people expect. A wall with three windows and a door can lose 15 percent of its face area, and 15 percent of a brick order is real money. Subtract the full opening area, then keep the waste allowance — cutting brick to fit around openings is exactly where waste comes from.
- What is a wythe?
- One vertical layer of masonry units, one unit thick. A single-wythe wall is one brick thick; a double-wythe or cavity wall has two, with ties between them, and needs twice the brick plus flashing, weeps and ties that a single wythe does not. This calculator counts one wythe, so double the result if your wall is two.
- Should I buy pre-blended mortar or mix my own?
- For anything under a few thousand units, pre-blended bags are worth the premium — the mix is consistent, which matters because mortar strength and colour both shift with the sand-to-cement ratio. Mixing from masonry cement and sand pays off on larger jobs, at roughly a ton of sand per eight bags of cement.