Free Cinder block calculator

How to estimate concrete blocks

Enter a shared wall height and add the length of each wall section. Under Openings & exclusions, deduct the door, window, or other opening area belonging to that section.

Select a nominal CMU preset or choose Custom actual face. The presets include 8 × 8 × 16 in, 6 × 8 × 16 in, and 8 × 8 × 8 in half blocks. For a custom block, enter actual face length and height. Check mortar-joint width and waste in the material settings.

Nominal size includes the joint

The count uses net wall area divided by the joint-inclusive face module. A standard full CMU face in this calculator is 15⅝ × 7⅝ inches. With a ⅜-inch joint, its repeating nominal face is 16 × 8 inches. Adding the joint again to an already nominal dimension would distort the estimate.

Results show units before waste, blocks to purchase after waste, opening deductions, and approximate courses. The 6-inch and 8-inch thick full-block presets share the same face coverage.

Use the result as a wall-unit allowance

This supports an initial block count for separate wall sections at one height. Half-block mode treats every unit as a half block; it does not produce a mixed bond schedule. Corners, special bond units, lintels, reinforcement, grout, and mortar are not included. Check the wall details before ordering. US and metric measurement modes are available.