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This concrete block and brick calculator tells you how many blocks or bricks you need to build a wall, along with an estimate of the mortar. Enter the wall length and height, subtract any doors or windows, choose your block or brick size and add a small allowance for breakage.
How to Use the Block and Brick Calculator
- Select the unit you are using: a standard 8×8×16 in concrete block (CMU), a US modular brick, or a UK/EU 440×215 mm block or 215×65 mm brick.
- Enter the total wall length and height. For several walls, add the lengths together if they are the same height.
- Enter the combined area of any doors, windows or other openings you will not fill.
- Add 5–10% extra for broken units and cuts at corners and openings.
- Optionally enter the price per block or brick to estimate the material cost.
Block and Brick Formula
The calculator divides the wall area by the face area of one unit, including the mortar joint around it:
Number of units = (Wall length × Wall height − Openings) ÷ Face area of one unit (with joint)
A standard US concrete block measures 7⅝ × 15⅝ in. With a ⅜ in mortar joint it covers 8 × 16 in, or 0.889 sq ft, so a wall needs 1.125 blocks per square foot. A US modular brick covers 8 × 2⅔ in with its joint, which works out to about 6.75 bricks per square foot. In the UK and Europe, a 215 × 65 mm brick with a 10 mm joint gives about 60 bricks per m² for a single-skin wall, and a 440 × 215 mm block gives about 10 blocks per m².
Worked Example: 20 ft × 8 ft Block Wall
- Wall area: 20 × 8 = 160 sq ft
- Blocks: 160 × 1.125 = 180 blocks
- With 5% extra: 180 × 1.05 = 189 blocks
- Mortar: roughly 8.5 cu ft per 100 blocks, so about 16 cu ft, or 24 bags of 80 lb mortar mix
Metric example: a brick garden wall 6 m long and 1 m high has an area of 6 m². At 59.3 bricks per m² that is 356 bricks, or 374 with 5% extra.
Units per Square Foot and Square Meter
| Unit | Size (actual) | Per sq ft | Per m² |
|---|---|---|---|
| US concrete block (CMU) | 7⅝ × 7⅝ × 15⅝ in | 1.125 | ≈12.1 |
| US modular brick | 3⅝ × 2¼ × 7⅝ in | 6.75 | ≈72.7 |
| UK/EU concrete block | 440 × 215 × 100 mm | ≈0.92 | ≈9.9 |
| UK/EU standard brick | 215 × 102.5 × 65 mm | ≈5.5 | ≈59.3 |
How Much Mortar Do I Need?
Mortar depends on joint thickness, the bond pattern and whether cores are filled, so treat these as starting points. A common rule for US block walls is about 8.5 cu ft of mortar per 100 blocks, and about 8.5 cu ft per 1,000 modular bricks. In the UK, allow roughly 0.5 m³ of mortar per 1,000 bricks and about 1 m³ per 1,000 blocks. Always buy a little extra; running out halfway through a course is frustrating.
Tips for Building Block and Brick Walls
- Order all units from the same batch so the color and size stay consistent.
- Block walls usually need a reinforced concrete footing. Use our concrete calculator to size it.
- Retaining walls, load-bearing walls and walls over about 3 ft (1 m) high often need engineering and a permit.
- Plan the wall length in multiples of the unit size where possible to reduce cutting.
- Double-skin (cavity) brick walls need twice the bricks shown for a single skin.
Frequently Asked Questions
How many blocks do I need per square foot?
A standard 8×8×16 in concrete block covers 0.889 sq ft including the mortar joint, so you need 1.125 blocks per square foot of wall, or 112.5 blocks per 100 sq ft.
How many bricks are in a square meter?
A standard UK/EU brick of 215 × 65 mm with 10 mm mortar joints gives about 60 bricks per square meter for a single-skin (half-brick) wall.
How many bricks per square foot?
US modular bricks laid with a 3/8 in joint need about 6.75 bricks per square foot of wall face.
How much extra should I order?
Add 5% for simple straight walls and up to 10% for walls with many corners, openings or cut units. Broken units in delivery are also common.
Does the calculator subtract doors and windows?
Yes. Enter the total area of openings in the openings field and it will be subtracted from the wall area before the count is calculated.
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