Concrete Block Calculator
Use nominal module dimensions that include the intended mortar joint. Subtract openings from gross wall area before the final block count is rounded up.
How to use this calculator
Enter the wall dimensions and add door or window openings.
Choose or enter the nominal block face dimensions.
Set the allowance and round the final quantity up to whole units.
Formula
Net wall area = gross area − openings. Units = ceil(net wall area ÷ nominal face area × (1 + allowance)).
Worked example
A 10 ft × 8 ft wall has 80 ft². Nominal 8 in × 16 in modules cover 0.889 ft² each, so about 90 units are needed before allowance.
Assumptions and limits
- Default nominal face is 8 in × 16 in.
- Default extra material is 5%.
- Bond pattern, pilasters, special shapes, and structural design are excluded.
Sources
Related calculators
Frequently asked questions
Why use nominal rather than actual block size?
Nominal dimensions include the mortar-joint module used to lay out wall coverage; actual manufactured dimensions are slightly smaller.
Can I use metric and US customary units in the Concrete Block Calculator?
Yes. Unit changes convert the same canonical measurement; they do not reinterpret or round your original value.
When does the calculator round?
The calculation keeps full precision internally and rounds only the displayed result. Whole packages are rounded up at the final step.
Last updated · formula-v1 · content-2026-08-14 · Trusty Calculator Editorial Team