Use the masonry module
A nominal block size describes a module that can include the mortar joint. This calculator asks for the actual unit length and height, then adds the entered joint thickness for counting. Its example 15⅝-inch × 7⅝-inch unit plus a ⅜-inch joint gives a 16-inch × 8-inch module.
Verify both the actual unit dimensions and the intended joints with the supplier. Do not add a mortar joint again to a dimension that already includes the nominal module.
Installed module = actual unit dimension + joint thickness
Count units without designing reinforcement
The tool estimates face units and a waste allowance. It does not estimate mortar bags, concrete grout, reinforcing steel, footings or weep-hole details. Those quantities depend on the selected masonry design.
A retaining wall made from ordinary hollow masonry units is not interchangeable with a dry-stacked segmental retaining system. Do not treat the unit count as permission to build an unreinforced wall. Have the masonry and foundation details established by a qualified professional.
Keep special units on the quote
Bond beams, corners, half blocks and other special units can replace ordinary units in the face count. Send the takeoff and the actual design drawings together when asking for a supplier schedule.
The calculator counts uniform courses. Openings, returns and foundation steps must be handled separately. A plan-specific block schedule is the final check before ordering.
References and scope
Arithmetic and worked examples are explained on our methodology page. These manufacturer references provide product-specific context, not approval of a generic wall. Accessed October 1, 2026.
- Allan Block: residential basic installation
- Allan Block: reinforcement installation
- Allan Block: residential retaining wall manual
Read the estimating and engineering limits, or send a correction.