Brick Calculator

How to use this calculator

1. Choose Metric or Imperial measurements.
2. Choose Bricks or Concrete blocks as the material.
3. Enter the wall length and height.
4. Choose the wall thickness and the brick or block type.
5. Add the size of any doors, windows or other openings.
6. Select a waste allowance.
7. The calculator estimates the bricks or blocks, and the mortar, required.

What do I need to enter?

• Measurement system — Metric (m, cm, mm) or Imperial (ft, in). Switching converts the dimensions you have entered.
• Material type — Bricks or Concrete blocks. It changes the unit sizes on offer and the mortar allowance per square metre.
• Wall length and Wall height — each above zero and up to 100 m, in the unit you pick.
• Wall thickness — single or double (single or double skin, leaf or wythe). Double doubles the count of bricks or blocks and the mortar.
• Brick type or Block type — the standard UK or US size, or a custom face length and height, each up to 1 m. Block thickness is shown for reference and never changes the count.
• Mortar joint — the gap around each unit, from zero up to 50 mm. It is added to the unit's face size.
• Openings — a count of doors and of windows (0 to 999 each) with a width and height for each, plus any other openings as one area. They are subtracted from the wall.
• Waste allowance — 0%, 5%, 10% or 15% extra for cuts and breakages.

What do the results show?

• Bricks to buy or Blocks to buy — the main figure, rounded up to a whole unit after waste, with the count before waste beneath it.
• Gross wall area and Opening area — shown once you add openings.
• Net wall area — the area left to build after subtracting openings.
• Mortar — an approximate volume, in m³ with litres alongside for metric or in ft³ for imperial.
• Working line — the sum written out: net area ÷ face area per unit, then waste, rounded up. If the openings cover the whole wall, a message asks you to reduce them.

How to calculate how many bricks you need

The calculator finds the wall area, subtracts doors and windows, then divides the remaining area by the working face area of one brick, including mortar joints. It applies the selected wall thickness and waste allowance before rounding the final quantity up to a whole brick.

Example: a 5 m × 1.8 m single-skin wall, standard UK brick

1. 5 × 1.8 = 9 m² of wall, with no openings to subtract.
2. The working face is (0.215 + 0.010) × (0.065 + 0.010) = 0.016875 m².
3. 9 ÷ 0.016875 = 533 bricks before waste.
4. With a 10% allowance, 533.3 × 1.10 rounds up to 587 bricks to buy.

Example: a 5 m × 2.4 m wall with one window, single skin and double skin

1. 5 × 2.4 = 12 m² of wall. A 1.2 m × 1.0 m window removes 1.2 m², leaving 10.8 m².
2. 10.8 ÷ 0.016875 = 640 bricks before waste.
3. With a 10% allowance, 640 × 1.10 = 704 bricks to buy for a single skin.
4. A double skin doubles the count to 1,280 bricks, or 1,408 bricks with 10% waste.

What size is a standard UK brick?

A standard UK brick measures 215 mm long × 102.5 mm deep × 65 mm high. Adding a 10 mm mortar joint to the length and the height gives the working face the calculator uses: 215 + 10 = 225 mm by 65 + 10 = 75 mm. With the joint on the depth as well, the co-ordinating size is 225 × 112.5 × 75 mm.

For a single-skin wall, this works out at around 60 bricks per square metre (1 ÷ 0.016875 = 59.3). A double-skin wall uses approximately twice as many bricks. The calculator uses the visible face of the brick, so the brick depth does not change the count.

What size is a standard UK concrete block?

Standard UK concrete blocks, sometimes called breeze blocks, are commonly 440 mm long × 215 mm high. They are available in different thicknesses, including 100 mm, 140 mm and 215 mm.

With a typical 10 mm mortar joint, the working face of a 440 mm × 215 mm block is 450 mm × 225 mm. This means one block covers approximately 0.101 m², so allow around 10 blocks per square metre of wall.

These uses are general and non-prescriptive. Block thickness, bond and wall design depend on the project and its structural requirements, so confirm the specification before ordering.

What size is a standard US concrete block?

In the United States, concrete blocks are commonly called concrete masonry units, or CMUs. A standard CMU is usually described by its nominal size of 8 × 8 × 16 inches.

The actual block is commonly about 7 5/8 inches high × 7 5/8 inches thick × 15 5/8 inches long. The block is made 3/8 inch smaller than its nominal dimensions so that mortar joints create an 8 × 8 × 16 inch module when laid.

With 3/8-inch mortar joints, a standard 8 × 8 × 16 inch CMU covers 128 square inches, or about 0.889 square feet. Allow approximately 1.125 blocks per square foot before openings and waste.

All three standard sizes share the same 8 × 16 inch nominal face, so they use the same 1.125 blocks per square foot. The listed thickness changes the wall thickness but not the block count per square foot of wall face for these standard 8 × 16 inch modules.

How do metric and imperial brick measurements compare?

The calculator converts every measurement into a single internal wall area before showing results in the selected measurement system.

How many bricks do I need for a cavity wall?

A cavity wall is two leaves with a gap between them. The gap does not change how many bricks or blocks the wall needs, so what matters is what each leaf is built from.

• Brick outer leaf and concrete block inner leaf, a common arrangement in UK houses: run the calculator once for bricks (about 60 per m²) and once for concrete blocks (about 10 per m²).
• Brick on both leaves: choose Double-skin for about 120 bricks per m². The 10.8 m² wall in the example above needs 1,408 bricks with 10% waste.

A solid wall one brick (215 mm) thick also uses about 120 bricks per m². Wall ties and cavity insulation are not counted. The number and spacing of ties depend on the cavity width and the design, so take them from the specification.

How much mortar do I need for bricklaying?

For single-skin brickwork the calculator allows 0.022 m³ of mortar per m² of wall, then adds your waste allowance. For the 9 m² example wall that is 9 × 0.022 × 1.10 = 0.22 m³ (218 L). A double skin takes twice as much. Blockwork uses 0.020 m³ per m² for each leaf.

That is an allowance, not a measurement. The Brick Development Association puts mortar at about 17.5% of stretcher-bond brickwork. A half-brick wall holds 0.1025 m³ per m², so the joints alone come to about 0.018 m³ per m². The brick allowance sits above that to leave room for mortar that never reaches a joint. The block allowance does not change with block thickness, so it runs high for thinner blocks.

Which mortar to use depends on the bricks, how exposed the wall is and the mortar designation in the specification, so this page leaves the mix to the specification. The Brick Development Association's Mortar for Brickwork guide covers cement, lime and sand mixes, masonry cement, air-entrained mixes and ready-mixed mortars. In the US, mortar for unit masonry is specified to ASTM C270.

How much sand and cement do I need for brickwork?

The calculator gives mortar volume, not bags. As a cross-check, the Brick Development Association says a tonne of ready-mixed lime and sand, gauged on site with the specified amount of cement, generally lays about 1,000 bricks. On that basis the 704 bricks in the window example would take roughly 0.7 tonnes of lime and sand mix.

Gauge the cement accurately and follow the supplier's instructions. The same guide warns that inaccurate gauging affects strength, durability and resistance to movement.

How much brick waste should I allow?

A waste allowance helps cover cuts, breakages, damaged bricks, colour selection and site losses. For straightforward work, 5% to 10% is a useful starting estimate. Consider a higher allowance for complex openings, detailed brickwork or projects with many cuts.

How much concrete do I need under the wall?

Need a concrete footing or base for this wall first? See the Concrete Volume Calculator.

Sources and standards

The figures and guidance on this page draw on the references below. British and American standards sit behind a paywall, so they are named but not linked.

• Designing Buildings Wiki: Brick sizes. Standard brick and co-ordinating sizes, with 10 mm mortar joints.
• Brick Development Association: technical guides. The Mortar for Brickwork guide is the source of the 17.5% joint share and the 1,000-bricks-per-tonne yield.
• GOV.UK: Structure, Approved Document A. Building Regulations guidance for England on the structure of walls and foundations. Read it, and ask a qualified professional, before building a load-bearing or retaining wall.
• Concrete Masonry & Hardscapes Association: technical resources. The US industry body for concrete masonry, formed from the National Concrete Masonry Association.
• Standards: BS EN 771-1 (clay masonry units), BS EN 771-3 (aggregate concrete masonry units), BS EN 998-2 (masonry mortar), ASTM C90 (loadbearing concrete masonry units) and ASTM C270 (mortar for unit masonry).

Frequently asked questions