How the calculation works
The formulas
Enter the exposed unit length and height. The modular face includes one horizontal and one vertical joint. Unit depth is the assumed wall thickness; this model uses one leaf in stretcher bond.
Net wall area = gross area − openings
Module area = (unit length + joint) × (unit height + joint)
Units = ceil(net area ÷ module area × (1 + waste/100))
Assumptions to check
- Single-leaf stretcher bond only; cavity walls, headers, piers, lintels, and special units need separate takeoffs.
- The count does not check stability, load capacity, or local wall requirements.
A worked example
10 m² with 390 × 190 mm blocks and 10 mm joints uses a 0.08 m² module: 125 units before waste, or 132 with 5% waste.