How to Calculate Bricks for a Wall: The Formula Explained

The basic formula

Number of bricks = wall width (m) × wall height (m) × bricks per square metre, then multiplied by 2 for a double-skin wall, then increased by your waste allowance. The detail is entirely in that middle figure, bricks per square metre, which depends on brick size and mortar joint thickness.

Step 1: measure the wall

Measure the width (left to right) and height (bottom to top) of the wall, in metres, and multiply them to get the area in square metres (m²). A garden wall that's 5m wide and 1.2m high is 5 × 1.2 = 6m².

Step 2: find bricks per square metre

This is where mortar joints matter. A single standard brick's raw footprint is 220mm × 110mm, but adding a 10mm mortar joint changes the effective spacing both between bricks in a row and between rows, in a way a simple footprint division doesn't capture. Rather than deriving this from scratch on site, use the proven South African industry figures, the same ones this site's calculator uses:

• Standard brick (220 x 110 x 75mm), single-skin, 10mm mortar joint: approximately 60 bricks per m2
• Standard brick, 8mm joint: approximately 62 bricks per m2 (tighter joint, slightly more bricks)
• Standard brick, 12mm joint: approximately 58 bricks per m2 (looser joint, slightly fewer bricks)
• Maxi brick (240 x 115 x 90mm), single-skin, 10mm mortar joint: approximately 42-45 bricks per m2
• Maxi brick, 8mm joint: approximately 46 bricks per m2
• Maxi brick, 12mm joint: approximately 41 bricks per m2

Step 3: account for double-skin walls

A double-skin wall (two brick layers with an air cavity between them for insulation and weatherproofing, typical of a South African external residential wall: an inner load-bearing leaf, a 50-100mm air cavity, and an outer weather-facing leaf) simply doubles the single-skin figure: double-skin bricks = wall m2 × bricks per m2 × 2.

Step 4: add a waste allowance

Construction always involves some loss: roughly 1-3% in transport and handling breakage, 2-4% laying waste (cutting, misplacement), and 1-2% rejected during sorting for quality. Standard industry practice is to add 5-10% to your calculated total: multiply by 1.07 for a 7% buffer, or 1.10 for a 10% buffer.

Complete worked example

Scenario: a double-skin external wall, 25m long, 2.8m high, standard brick, 10mm mortar joint (a typical South African residential perimeter section).

1. Wall area: 25m × 2.8m = 70m2
2. Bricks per m2 (standard, single-skin, 10mm joint): 60
3. Double-skin: 70m2 × 60 × 2 = 8,400 bricks (minimum, before waste)
4. Add a 7% waste buffer: 8,400 × 1.07 = 8,988 bricks
5. Round up to a clean order quantity: 9,000 bricks, or 18 pallets at 500 bricks per pallet

Adjusting for openings and complex walls

A standard door (0.9m wide x 2m high = 1.8m2) removes about 1.8 x 60 x 2 = 216 bricks from a double-skin wall's total. A large window (2m x 1.5m = 3m2) removes about 3 x 60 x 2 = 360 bricks. Many builders add back a small 2-3% allowance for the lintel and reinforcement needed around an opening, so the net saving ends up slightly less than the pure opening area suggests.

Curved or arched walls need wedge-shaped and cut bricks: add 10-15% for a simple curve, 15-25% for a complex arch, on top of the straight-wall calculation. For a sloped or tapered wall (a gable, for example), use the average of the start and end height as your height input: a gable that starts at 2.5m and tapers to 0m at the peak averages to 1.25m.

Common calculation errors

Three mistakes account for most brick-order shortfalls or overspends:

• Using a single brick's raw dimensions instead of the bricks-per-m2 industry figure: dividing 10m2 by a 0.22m x 0.11m footprint gives roughly 413 bricks, dramatically too low, because it ignores mortar joints entirely. The correct figure (10m2 x 60/m2 = 600 bricks) is nearly 50% higher.
• Forgetting a wall is double-skin: ordering the single-skin quantity for a wall that actually needs two leaves is a shortfall of exactly half, discovered mid-project.
• Confusing linear metres with square metres: a supplier or plan quoting '10 linear metres of wall' is only giving you length. You still need the height to get an area.

Quick-reference table

A 10m2 wall in standard brick, single-skin, needs 10 x 60 = 600 bricks. The same wall, double-skin, needs 10 x 120 = 1,200 bricks. See the brick sizes and types page if you're not sure which brick format your project needs.

A sanity check using laying speed

Experienced bricklayers typically lay 300-400 bricks per day on a single-skin wall, or 150-200 bricks per day on a double-skin wall. If your calculated total implies an unrealistic timeline (10,000 bricks at 150/day is roughly 67 days of laying), it's worth double-checking your wall area and skin count before ordering.

Working out your own numbers

Nothing on this page or in the calculator's fields is sent anywhere, every figure above and every result the calculator produces is computed locally in your own browser. See the privacy policy for the full detail.