Brick Calculator
Enter the wall size, subtract doors and windows, choose a brick size and mortar joint, and get the number of bricks to buy, the mortar volume and how many bags of mortar mix you need, in metric or imperial units.
Wall
Brick and mortar joint
Waste, bags and cost
How to use the Brick Calculator
- Pick metric or imperial units at the top.
- Enter the wall length and height, choose single or double leaf, and add any doors or windows to subtract.
- Choose a brick size or type your own dimensions, and set the mortar joint (10 mm or 3/8 in is standard).
- Set the waste allowances and mortar bag size, plus prices if you want a cost estimate.
- Press Calculate to see bricks to buy, bricks per square metre or foot, mortar volume and bags.
Brick and mortar formulas
- Bricks per m² = 1 ÷ ((brick length + joint) × (brick height + joint)), multiplied by 2 for a double-leaf wall.
- Net wall area = length × height − openings.
- Bricks to buy = net area × bricks per m² × (1 + waste %), rounded up.
- Mortar per brick = (L + j)(H + j) × D − L × H × D, where D is the brick depth. Double-leaf walls also get a collar joint of area × j.
- Bags = mortar volume × (1 + mortar waste %) ÷ bag yield.
Worked example: 10 m garden wall
- Wall: 10 m × 2 m = 20 m², single leaf, no openings, UK bricks (215 × 102.5 × 65 mm) with 10 mm joints.
- Bricks per m²: 1 ÷ (0.225 × 0.075) = 59.26. Bricks: 20 × 59.26 = 1,185.2; plus 5% waste = 1,244.4, so buy 1,245 bricks.
- Mortar per brick: 0.225 × 0.075 × 0.1025 − 0.215 × 0.065 × 0.1025 = 0.000297 m³. For 1,185.2 bricks that is 0.352 m³; plus 15% = 0.405 m³.
- 25 kg bags at about 13.2 litres each: 405 ÷ 13.2 ≈ 30.8, so 31 bags.
Common brick sizes
| Brick | Size (L × D × H) | Joint | Bricks per m² (single leaf) | Bricks per ft² |
|---|---|---|---|---|
| UK standard | 215 × 102.5 × 65 mm | 10 mm | 59.3 | 5.51 |
| US modular | 7⅝ × 3⅝ × 2¼ in | ⅜ in | 73.8 | 6.86 |
| US standard | 8 × 3⅝ × 2¼ in | ⅜ in | 70.5 | 6.55 |
| Australian standard | 230 × 110 × 76 mm | 10 mm | 48.4 | 4.50 |
| European NF | 240 × 115 × 71 mm | 10 mm | 49.4 | 4.59 |
Frequently asked questions
How many bricks are in a square metre?
With UK standard bricks (215 × 65 mm face) and 10 mm joints, each brick plus mortar covers 225 × 75 mm = 0.016875 m², so a single-leaf wall needs 1 ÷ 0.016875 ≈ 59.3 bricks per m², usually rounded to 60. A double-leaf wall needs about 119.
How many bricks per square foot?
US modular bricks (7⅝ × 2¼ in) with ⅜ in joints cover 8 × 2⅝ = 21 in² each, so you need 144 ÷ 21 ≈ 6.86 bricks per ft² for a single wythe. Many tables round this to 7, or quote 6.75 when 3 courses are laid to exactly 8 inches.
How do I calculate how many bricks I need?
Multiply wall length by height, subtract the area of doors and windows, then multiply by the bricks per square metre or foot. Add 5 to 10% for breakages and cuts and round up. A 10 × 2 m UK wall: 20 m² × 59.26 = 1,185 bricks, plus 5% = 1,245.
How much mortar do I need for bricks?
Each brick needs mortar for one bed joint and one head joint: (L + j)(H + j) × depth − L × H × depth. For UK bricks that is about 0.0003 m³ per brick, or roughly 0.018 m³ per m² of single-leaf wall before waste. Add 10 to 20% for droppings and filling frogs.
How many bricks does a bag of mortar lay?
A 25 kg bag of pre-mixed mortar makes about 13 litres and lays roughly 40 to 45 UK bricks. An 80 lb bag makes about 0.67 ft³ and lays roughly 80 US modular bricks with ⅜ in joints in theory, fewer in practice once waste is included.
What is the standard mortar joint size?
10 mm in the UK, Europe and Australia, and ⅜ inch (9.5 mm) in the US. Joints between about 8 and 12 mm are common; thicker joints use more mortar and fewer bricks.
What waste percentage should I use for bricks?
5% is typical for straight walls with whole bricks. Use 10% or more for walls with many corners, openings, decorative bonds or when cutting a lot of bricks.