Brick Calculation Guide: How Many Bricks Do You Need?

Brick counting looks simple — divide wall area by brick face area — but the number that actually matters is the effective footprint each brick occupies once it's laid, which is larger than the brick itself because of the surrounding mortar joint.

Add your mortar joint thickness (commonly 10mm) to both the brick's length and height before calculating its footprint. A standard modular brick at 215mm × 65mm with a 10mm joint effectively occupies 225mm × 75mm once laid — noticeably more than its raw dimensions suggest.

Divide your net wall area (gross area minus doors and windows) by this effective footprint to get a raw brick count, then add a wastage allowance of around 5% for cutting at corners and openings, plus breakage during handling and transport.

For cavity or double-leaf walls, run the calculation separately for each leaf and sum the results — the two leaves are rarely identical if one uses a different brick or block type. And remember: this calculation gives you brick count and, indirectly, mortar volume — it doesn't account for reinforcement, wall ties, or lintels over openings, which are estimated separately.