Brick and Block Calculator
Calculate how many bricks or blocks a wall needs, including walls more than one unit thick, along with the mortar between them.
Formula
One unit occupies its face area plus one joint in each direction. The number of leaves comes from the wall thickness divided by the unit depth plus a collar joint.
- Net wall area (m²) = (L × H) − openings
- Leaves = round( Wall thickness ÷ (Unit depth + joint) ), minimum 1
- Area per unit face (m²) = (Unit length + joint) × (Unit height + joint)
- Units per m² = Leaves ÷ Area per unit face
- Units = Net area × Units per m² × (1 + wastage % ÷ 100)
- Mortar (m³) = Wall volume − (Units × unit length × unit height × unit depth)
Worked example
A 10 m × 2.7 m wall in 215 × 65 × 102.5 mm bricks, 102.5 mm finished thickness, 10 mm joints, 5% wastage, no openings.
- Net area = 10 × 2.7 = 27 m²
- Leaves = round(102.5 ÷ (102.5 + 10)) = round(0.91) = 1
- Area per brick face = 0.225 × 0.075 = 0.016875 m²
- Bricks per m² = 1 ÷ 0.016875 = 59.3
- Net bricks = 27 × 59.3 = 1600
- With 5% wastage = 1680 bricks
About 1680 bricks. The same wall at 215 mm thickness works out at 2 leaves and roughly 3360 bricks.
Assumptions and limitations
- The number of leaves is derived from the wall thickness and unit depth. This is accurate for walls built as separate leaves. Bonded walls using headers give a similar total unit count but arrange the units differently.
- The joint thickness is added once to the length and once to the height of each unit, which is the standard way of working out coverage.
- Units are treated as solid for the mortar calculation. Hollow blocks and perforated bricks change the mortar figure.
- No allowance is made for bonding patterns that need cut units at ends and openings beyond the general wastage.
What this calculator does not do
- Does not design the wall, check slenderness, or verify any structural requirement.
- Does not handle cavity construction as two separately specified leaves — run each leaf as its own calculation if the units differ.
- Does not include wall ties, insulation, damp-proof courses, lintels or reinforcement.
Practical tips
- Bricks per square metre is the number worth memorising for your local unit size. For 215 × 65 mm faces with 10 mm joints it is about 59 per m² per leaf.
- For a cavity wall with different inner and outer units, run the calculator twice — once per leaf — rather than entering the overall thickness.
- Increase wastage for walls with many openings or a complex bond — cutting generates far more waste than a plain run.
- Order all units for one wall in a single delivery where you can. Colour and texture vary between production batches, and the difference shows.
Frequently asked questions
How many bricks are in a square metre?
For a standard 215 × 65 mm brick face with 10 mm joints, roughly 59 bricks per square metre per leaf. A one-brick wall is two leaves, so about 118 per square metre.
Does this work for a wall thicker than one brick?
Yes. Enter the finished wall thickness and the unit depth separately, and the calculator works out how many leaves that is and multiplies the unit count accordingly.
What about a cavity wall?
A cavity wall is two leaves with an air gap, not a solid thickness. Run each leaf as a separate calculation using its own unit and thickness, rather than entering the overall wall thickness including the cavity.
How much mortar do bricks need?
For a single-leaf brick wall with 10 mm joints, roughly 0.018 m³ of mortar per square metre of wall. The calculator derives it from your actual unit size and joint thickness rather than a fixed rate.
Related calculators
- Mortar Calculator Convert a mortar volume into cement, sand and water quantities for a given mix ratio.
- Plaster Calculator Calculate plaster or render volume for a wall, and the cement and sand it needs.
- Paint Calculator Work out how much paint a wall or room needs, allowing for coats, openings and the coverage rate on the tin.
- Area Calculator Calculate the area of a rectangle, triangle, circle or trapezoid, with results in metric and imperial units.
Estimating tool, not a design. This calculator works out quantities from the dimensions you enter. It does not size any structural member, verify a design, or confirm compliance with any building code. Check every result against your project specification and applicable local standards, and involve a qualified engineer where the work requires one.