How many CMU blocks do I need? Block count from plans
For standard 8×8×16 concrete block, the count is simple: 1.125 blocks per square foot of wall. The work is getting the net wall area right.
Why 1.125?
A nominal 8×16 block face, including the 3/8" mortar joint, covers 8" × 16" = 128 sq in, or 0.889 sq ft. One square foot ÷ 0.889 = 1.125 blocks.
1. Wall area
Wall length × wall height, for each CMU wall. Heights come from the elevations or wall sections — check whether the wall runs to a bond beam, the roof deck, or a parapet.
2. Subtract openings
Unlike drywall, subtract every door and window opening from CMU area: each one is block you won't lay.
3. Multiply and add waste
Net area × 1.125, then add about 5% for breakage and cuts.
Gross: 160 × 12 = 1,920 sq ft · openings: 63 + 64 = 127 sq ft · net: 1,793 sq ft.
1,793 × 1.125 = 2,017 blocks × 1.05 ≈ 2,118 blocks.
4. Special blocks
Count separately: bond beam block (usually a course at the top and at floor lines), lintel block over openings, and corner/end blocks. The structural notes and wall sections say where bond beams and grouted cells go.
5. Mortar
A common rule of thumb is roughly 8–9 bags of masonry cement per 100 block — confirm against your supplier's numbers.
ReadMyBlueprint measures CMU wall length and area straight from the plan's own geometry, so the area you multiply is measured, not guessed.
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