Hong Life CalculatorsUnderstanding the brick and block calculator — concept and principle
This calculator estimates how many bricks or blocks you need for a wall of a given face area, including a waste allowance, together with an approximate volume of mortar. Use it for garden walls, extensions, piers and repairs before ordering materials.
How it is calculated
- Bricks per m² = 1 ÷ [(brick length + joint) ÷ 1,000 × (brick height + joint) ÷ 1,000]. Sizes are in mm.
- Bricks = wall area × bricks per m² × (1 + waste% ÷ 100), rounded up.
- Mortar (m³) ≈ wall area × joint share of the face × wall thickness × 1.25. The joint share is 1 − (brick face ÷ module face); the 25% covers frogs, waste and uneven joints.
The count is for a single-leaf wall laid in stretcher bond with the brick's length and height on the face (a "half-brick" wall about 102.5 mm thick for UK bricks). A one-brick thick wall needs roughly twice as many.
The principle
On the face of the wall each brick occupies its own size plus one joint width in each direction, because each joint is shared half by the brick on either side. For the UK standard brick of 215 × 65 mm with 10 mm joints, the coordinating size is 225 × 75 mm, so one brick covers 0.016875 m² and about 59.3 bricks fill a square metre, the familiar "60 per m²". Mortar fills the gaps between those modules: about 17.2% of the face, which for a 102.5 mm thick half-brick wall is 0.0176 m³ per m², or about 0.022 with the 25% margin.
Worked example
- Wall area 10 m², brick 215 × 65 mm, 10 mm joint, 5% waste.
- Module = 0.225 × 0.075 = 0.016875 m².
- Bricks per m² = 1 ÷ 0.016875 ≈ 59.26.
- Bricks = 10 × 59.259 × 1.05 = 622.2, rounded up to 623 bricks.
- Mortar: joint share = 1 − (215 × 65) ÷ (225 × 75) = 0.1719; 10 × 0.1719 × 0.1025 × 1.25 ≈ 0.22 m³.
| Brick length (mm) | Bricks |
|---|---|
| 53.8 | 2,197 |
| 108 | 1,192 |
| 161 | 818 |
| 215 | 623 |
| 269 | 503 |
| 322 | 422 |
| 430 | 319 |
How to read the result
Bricks are often sold in packs or by the thousand, so round up to the supplier's unit. A waste figure of about 5% suits plain walls; allow more for many corners, openings, cut bricks or soft handmade bricks. For concrete blocks of 440 × 215 mm with 10 mm joints the same formula gives 10 blocks per m²; enter the block width as the wall thickness so the mortar follows.
Common mistakes
- Entering the wall's length instead of its area, or forgetting to subtract windows and doors.
- Forgetting that a cavity wall or one-brick wall has two leaves of brick.
- Leaving the wall thickness at 102.5 mm for blocks or thicker walls.
Frequently asked questions
How many bricks are in a square metre?
About 60 for UK standard bricks with 10 mm joints in a half-brick wall, and about 120 for a one-brick wall.
How much sand and cement is in 0.22 m³ of mortar?
That depends on the mix ratio; use a mortar mix calculator with your chosen cement-to-sand ratio.
Do I need to subtract openings?
Yes. Subtract the area of each window and door from the wall area before calculating.
Sources: BS EN 771-1: Specification for masonry units, Clay masonry units, BSI/CEN · Brick Development Association (UK), technical guidance on brickwork