calcs.homes
calcs.homes
Enter your wall's length and height to get standard concrete block (CMU) count, mortar bags, and estimated cost.
Estimate only — assumes standard 8 x 16 in (US) or 390 x 190 mm (EU) block with 3/8 in mortar joints.
We multiply wall area (length × height) by 1.125 blocks per square foot — the standard coverage rate for an 8 x 16 in concrete block laid with a 3/8 in mortar joint (12.5 blocks per square meter for a 390 x 190 mm block in metric) — add 5% waste, and round up to a whole block. Mortar bags use a separate rule of thumb of about 3 bags per 100 blocks, also rounded up.
The 1.125 blocks-per-sq-ft figure comes from the block's actual face dimensions plus a standard joint width, both fairly consistent across CMU construction, so it's the same shortcut masons use to rough out a material order before a detailed takeoff. The waste allowance covers broken units and the extra cuts needed at corners and openings, and rounding both blocks and mortar bags up avoids a mid-job supply run over a fraction of a unit.
Multiply wall area (length × height) by 1.125 for standard 8 x 16 in block. Enter your dimensions above for the exact count with a waste allowance included.
About 3 bags of mortar mix per 100 blocks is a common rule of thumb, though joint thickness and block face shell design can shift this.