The math behind your estimate
The inputs, allowance, and rounding stay visible.
- Wall area
- Gross = Length × Height, summed over every wall
- Net area
- Net = Gross − openings (Width × Height × quantity)
- Module
- Effective size = (brick length + joint) × (brick height + joint)
- Bricks
- Bricks = Net area ÷ effective size, × (1 + waste %), rounded up
- Packs
- Packs = Bricks ÷ bricks per pack, rounded up
Assumptions
- Counts are for a single-wythe (half-brick) wall laid in stretcher bond — one brick face per unit of wall area. A double-wythe or solid wall needs roughly twice the bricks; header courses and decorative bonds change the count further.
- The mortar joint you enter is applied to both the bed (horizontal) and perpend (vertical) joints, so each brick occupies its face size plus one joint in each direction. This is why a 7⅝ in brick with a ⅜ in joint is described as an 8 in module. Nominal brick tables assume a slightly larger bed joint to make courses come out at round numbers — if you need to match a published nominal figure exactly, adjust the joint accordingly.
- Brick sizes vary by country and by manufacturer. The presets are conveniences, not standards — measure your actual brick, or take the dimensions from the supplier's datasheet.
- Mortar quantity is not estimated here. It depends on joint thickness, bond and wall thickness, and is best taken from your mortar supplier's coverage figures.
Scope note
Quantity estimation only. This tool does not design walls: wall thickness, footings, reinforcement, lateral support and height limits are structural and code matters for your local building authority or engineer.
Frequently asked questions
- How many bricks are in a square metre or square foot?
- With a standard UK brick (215 × 65 mm) and a 10 mm joint you get about 59 bricks per square metre of single-wythe wall. With US modular brick (7⅝ × 2¼ in) and a ⅜ in joint it works out at about 6.86 per square foot. You will often see 6.75 quoted instead — that figure assumes the nominal 2⅔ in course height, which needs a slightly fatter bed joint of about 7/16 in. This calculator uses the dimensions you actually enter rather than a rule of thumb.
- Does the mortar joint really change how many bricks I need?
- Yes, and by more than people expect. A ⅜ in joint adds about 5% to each brick's footprint in both directions. Ignoring it over a large wall can leave you several hundred bricks short.
- What is the difference between nominal and actual brick size?
- Actual is the brick you can hold; nominal includes the mortar joint so the numbers come out round. A US modular brick is actually 7⅝ × 2¼ in but is called 8 × 2⅔ in nominal. Enter the actual size here and set the joint separately — the calculator derives the module itself.
- How many extra bricks should I order?
- 5% for straight runs with few cuts, 10% where there are several openings and corners, and 15% for curves, arches or decorative bonds. Bricks also arrive with some breakage, and matching a colour batch later is difficult — ordering slightly long is the cheaper mistake.
Sources
- US modular brick nominal/actual dimensions (Brick Industry Association conventions)
- UK/AU standard brick format (215 × 65 mm with 10 mm joint)