Concrete Block Calculator
Enter your wall's length and height along with your block dimensions to estimate the rows and total blocks needed.
How concrete block quantities are estimated
This calculator converts your wall's length and height to inches, then divides by the block's width and height to find how many blocks fit in one row and how many rows are needed to reach the target wall height, rounding up each time since partial blocks still require a full block.
Standard concrete masonry units (CMU) are commonly 16 inches wide by 8 inches tall (nominal dimensions including the mortar joint), though block sizes vary — always confirm your specific block's dimensions before ordering.
Frequently asked questions
What does "nominal dimensions" mean for concrete blocks?
Nominal dimensions include the thickness of a standard mortar joint, so the actual block itself is typically 3/8 inch smaller in each dimension than its nominal size (a "16x8" block is actually about 15 5/8 x 7 5/8 inches), with the mortar joint making up the difference.
Does this account for corner blocks or half blocks?
No — this gives a straightforward count of standard full blocks based on area. Corner units, half blocks for running bond offsets, and any specialty blocks should be factored in separately based on your wall's specific layout.
Should I order extra blocks beyond this estimate?
Yes — it's standard practice to order 5-10% extra to account for cuts, breakage, and layout adjustments, especially for walls with openings, corners, or non-standard lengths.