Concrete & masonry
Concrete Block Calculator
Enter your wall size, block dimensions and any openings to estimate how many concrete blocks or CMUs you need. Optional fields keep price and block-fill estimates separate.
YOUR MATERIAL ESTIMATE
A clearer quantity starts here.
Enter your measurements, check the units and calculate. Your result will include the assumptions and rounding steps.
Show calculation
THE WORKFLOW
How to use this concrete block calculator
- Enter wall length and height, then choose nominal block dimensions or custom dimensions.
- Subtract total opening area and enter your optional waste allowance.
- Calculate exact blocks and whole blocks to order; add optional price or fill data only if needed.
Formula & assumptions
Net wall area = gross wall area − openings. Exact blocks = net area / nominal face area. Order blocks = round up(exact blocks × (1 + waste / 100)).
Use nominal modular face dimensions, including the joint allowance, rather than actual face dimensions. Area-based counts do not plan bond patterns, cuts or corner units. Optional fill uses user-supplied void volume per installed whole-block equivalent, not purchased spare blocks.
See methodology and sources →AN ARITHMETIC EXAMPLE, NOT A RECOMMENDATION
Worked example
Example only: a 16 × 8 ft wall with no openings, 16 × 8 in nominal faces and no extra.
- Gross wall area128 ft²
- Gross wall area11.892 m²
- Opening area0 ft²
- Opening area0 m²
Example calculation
Net wall: 11.891589 − 0 = 11.891589 m². Divide by nominal face 0.08258 m² = 144 blocks. Apply 0% extra, then round up 144 to 144.
Common questions
Does the count include openings?
Yes, subtract their total measured area in Advanced options. Openings cannot exceed the gross wall area.
Why use nominal block dimensions?
Nominal modular face dimensions include the joint allowance. Actual unit dimensions are smaller; use the module specified for your project.
Estimates only. Verify measurements and manufacturer packaging/yields. Project conditions vary. This tool does not provide structural engineering advice. Read the disclaimer.