The Block CalculatorHow does this concrete block calculator work?
Enter the overall length and height of your wall, then the face size of one concrete block. The calculator converts both to the same unit, divides the wall area by the block face area and rounds up. Add a price per block and it multiplies the count to give a material budget. Every field accepts metric or imperial units, so you can mix a wall measured in feet with blocks sold in inches.
Common concrete block sizes
- US nominal 8″ × 8″ × 16″ – actual size 7⅝″ × 7⅝″ × 15⅝″; the extra ⅜″ is taken up by the mortar joint. Enter 16 × 8 inches to include the joint.
- Metric 440 × 215 mm face – common in the UK and Europe (the joint-inclusive coordinating size is 450 × 225 mm).
- 400 × 200 mm – widely used in Asia, Africa and the Middle East, in 100–200 mm thicknesses.
Formula used
Total Blocks = (Wall Length × Wall Height) ÷ (Block Length × Block Height)The result is always rounded up to the next whole block, because you can’t buy part of one. Wall thickness is shown in the diagram but does not change the count for a single-wythe wall.
Example
Scenario: A wall 10 m long and 2 m high, built with concrete blocks measuring 40 cm × 20 cm (0.4 m × 0.2 m).
Wall area: 10 m × 2 m = 20 m²
Block face area: 0.4 m × 0.2 m = 0.08 m²
Final result: 20 ÷ 0.08 = 250 concrete blocks. Add 5–10% for cuts and breakage when you order.
Frequently asked questions
How many concrete blocks are in a square meter?
With 400 × 200 mm blocks (joint included) you need 12.5 blocks per m². With US 8″ × 16″ blocks you need 1.125 blocks per square foot, or about 12.1 per m².
Should I include the mortar joint in the block size?
Yes. Use the nominal (joint-inclusive) size, such as 16″ × 8″ rather than 15⅝″ × 7⅝″, so the joint area is not counted as extra blocks.
How much extra should I order?
Most builders add 5–10% for cuts, breakage and openings that need half blocks. Complex walls with many corners may need more.
Last updated: . Results are estimates — see our disclaimer.