Brick/Block Calculator
Calculate brick or block quantities and mortar for a masonry wall.
About Brick/Block Calculator
Masonry is set out on the module size rather than the unit size, because each unit carries one joint with it. Mortar volume follows from the difference between the module area and the unit face area. Ignoring the joint overstates unit counts by around 15 per cent on standard brick, which is the difference between one delivery and two.
Formula
Brick/Block
Units per m² = 1 ÷ ((length + joint) × (height + joint)); mortar fills the remainder
- module size
- Unit dimension plus one mortar joint, which is what actually repeats
- joint
- Mortar thickness, typically 10 mm
Worked example
With the default values below, Brick/Block Calculator returns Units Required of 2,489. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Wall areaminimum 0 m2
- 40 m2
- Unit lengthminimum 50 mm
- 215 mm
- Unit heightminimum 20 mm
- 65 mm
- Mortar joint thicknessaccepts 0–30 mm
- 10 mm
- Waste allowanceaccepts 0–50 %
- 5 %
Results
- Units Required
- 2,489
- Units per Square Metre
- 59.26
- Mortar Volume
- 0.4468 m3
- Mortar Bags at 25 kg
- 38
- Units Covered by Waste Allowance
- 118
Step by step
- 1Values used
- 2Brick/Block
- 3Units Required= 2,489
- 4Units per Square Metre= 59.26
- 5Mortar Volume= 0.4468 m3
- 6Mortar Bags at 25 kg= 38
- 7Units Covered by Waste Allowance= 118
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Brick/Block calculated?
Units per m² = 1 ÷ ((length + joint) × (height + joint)); mortar fills the remainder Masonry is set out on the module size rather than the unit size, because each unit carries one joint with it. Mortar volume follows from the difference between the module area and the unit face area.
Why does Brick/Block matter?
Ignoring the joint overstates unit counts by around 15 per cent on standard brick, which is the difference between one delivery and two.
What values do I need to enter?
This calculator takes 5 inputs: Wall area, Unit length, Unit height, Mortar joint thickness, Waste allowance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.