Concrete Block Calculator
Use this concrete block calculator to estimate the number of blocks needed to build a wall with specific dimensions, as well as to calculate the costs.
Blocks needed198180 to cover it, plus 10% waste, rounded up
Exact requirement180 blocks
Each block covers0.8889 sq ft0.08258 m²
Wall area after deductions160 sq ft14.8645 m²
Per square foot1.125 blocks
Nominal face size16 × 8 inunit plus one mortar joint
Actual unit size15.625 × 7.625 × 7.625 in
Mortar needed16.5 cu ftabout one cubic foot per 12 blocks
Bags of mortar mix2580 lb bags, 0.66 cu ft each
The method
units = wall area ÷ nominal face area, plus waste
Nominal size is what counts
A US modular brick measures 7⅝ × 2¼ inches, but you lay it on a ⅜-inch mortar joint, so it occupies an 8 × 2⅔ inch space in the wall. Divide a square foot by that and you get 6.75 bricks — which is why suppliers quote “about 7 per square foot”.
Concrete block works out even more neatly: a nominal 16 × 8 inch face is 128 square inches, so it is exactly 1.125 blocks per square foot.
The mortar figures are rules of thumb — roughly a cubic foot per 30 bricks or 12 blocks — and they vary with joint thickness and how much you waste on the board.