Concrete Block Calculator
This concrete block calculator finds how many blocks a wall needs from the wall area and the block size, with a waste allowance. Enter the numbers and the concrete block calculator returns the block count and blocks per square meter. It works as a cinder block calculator, a cmu block calculator, and a cement block calculator, since the math is the same whatever you call the block.
Results
The Concrete Block Calculator is part of our Materials Estimating collection. Browse more materials estimating to size, convert, and check your work alongside this tool.
What the concrete block calculator does
Ordering block for a wall means matching the wall area to how much one block covers, and this concrete block calculator does exactly that. Enter the wall area and the block dimensions and it returns the count, plus a waste margin for cuts and breakage. As a cinder block calculator or cmu block calculator it treats every standard unit the same way, so whether you call it a cinder block, a concrete masonry unit, or a cement block, the concrete block material calculator, or cinder block concrete calculator, gives the number to order. It doubles as a cement block estimator and cmu block estimator.
How the concrete block calculator counts blocks
The math behind any cinder block calculator is area division. The face area of one block is its length times its height, and the number of blocks is the wall area divided by that face:
The concrete block calculator then multiplies by the waste factor for cuts around openings and corners. A standard concrete masonry unit calculator uses a 390 by 190 mm block, which gives close to 12.5 blocks per square meter before waste, the figure a cmu block calculator returns by default.
Concrete block calculator example
A wall of 20 m² built from standard 390 by 190 mm blocks with a 5% waste allowance. The block face is 0.0741 m², so:
The concrete block calculator returns 284, and shows about 13.5 blocks per square meter. Enter your own wall area and the cinder block calculator gives the count the same way.
How to use the concrete block calculator
Enter the total wall area, then the length and height of one block, and a waste allowance. The concrete block calculator divides the wall by the block face to find the count and rounds up. To size a specific job, use it as a concrete block wall calculator by entering the wall area you measured; as a cmu block calculator it handles standard 390 by 190 mm units, and as a cement block calculator it accepts any size you type.
Reading the concrete block calculator result
The block count is what to order; the blocks-per-square-meter figure lets you scale quickly for other walls. The waste allowance is not padding, since cutting blocks around windows, doors, and corners always wastes some, and a broken block on site is common. If you plan to fill the cores, pair this with a block fill calculator for the concrete volume. For structural weight, a concrete block weight calculator multiplies the count by the unit weight.
When to use the concrete block calculator
- Ordering block for a wall with the concrete block material calculator
- Sizing a garden or retaining wall with the cinder block wall calculator, a handy calculator for block wall jobs
- Estimating a build in standard units with the cmu block calculator
- Pricing a job after the cement block calculator gives the count
- Estimating a wall build with the concrete block wall estimator
Common concrete block calculator mistakes
- Not subtracting openings. Enter the net wall area, or the concrete block calculator overstates the count.
- Nominal vs actual size. Use the coordinating size with the mortar joint so the cmu block calculator matches real coverage.
- Forgetting core fill. A reinforced wall also needs a block fill calculator for the concrete.
Tips for accurate results
- Subtract large openings from the wall area before using the concrete block calculator.
- Use the coordinating block size that includes the mortar joint.
- Add 5% waste, more for walls with many corners and openings.
Getting the concrete block calculator inputs right
The count from any concrete block calculator is only as good as the wall area you feed it, so measure carefully and subtract large openings. For a wall with a door and windows, work out the gross area, then take off the opening areas before entering the figure, since blocks are not laid where the glass and frames go. Small openings can be left in as part of the waste buffer. The other input that matters is the block size: a nominal 400 by 200 mm block and an actual 390 by 190 mm block with a 10 mm mortar joint cover almost the same wall, which is why a cmu block calculator built around the coordinating size gives realistic counts.
Filling cores and weight with the concrete block calculator
Two follow-on questions come up on nearly every block job. First, filled cores: reinforced walls have their hollow centers filled with concrete, so once the cinder block calculator gives the count you need a block fill calculator to find the concrete volume for those cores. Second, weight: a standard hollow concrete block weighs roughly 15 to 20 kg, so a concrete block weight calculator multiplied by the count tells you the load on the footing and how much material the crew will handle. Planning both alongside the block count turns a rough guess into a complete material and labor estimate.
Concrete block calculator chart
Blocks per square meter and per 10 m² wall for common block sizes, before waste, from the concrete block calculator:
| Block size | Face area | Blocks per m² | Blocks per 10 m² |
|---|---|---|---|
| 390 × 190 mm | 0.074 m² | 13.5 | 135 |
| 440 × 215 mm | 0.095 m² | 10.6 | 106 |
| 400 × 200 mm | 0.080 m² | 12.5 | 125 |
| 200 × 200 mm | 0.040 m² | 25.0 | 250 |
Concrete Block Calculator FAQ
How many concrete blocks do I need?
Divide the wall area by the face area of one block, then add waste. The concrete block calculator does this and returns the count for cinder, cmu, or cement blocks.
How many blocks are in a square meter?
A standard 390 by 190 mm block gives about 13.5 per square meter with mortar joints. The cmu block calculator shows the figure for whatever block size you enter.
Is a cinder block the same as a concrete block?
For counting, yes. Cinder block, cmu, and cement block are counted identically, so this cinder block calculator and a concrete masonry unit calculator give the same number for the same size.
What waste allowance should I use?
About 5% for a simple wall, more with many openings or corners. The concrete block calculator adds your allowance so the order covers cuts and breakage.