Calculate standard 8x8x16 CMU blocks, mortar bags, vertical rebar, and core fill grout for masonry foundation and retaining walls.
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A concrete block calculator determines the quantity of standard 8"×8"×16" Concrete Masonry Units (CMU) needed to build retaining walls, foundation stem walls, and structural masonry enclosures. It computes blocks, mortar bags, vertical rebar, and core fill grout.
\text{Blocks} = (L \times H \times 1.125) \times 1.05, \quad \text{Mortar Bags (70lb)} = \left\lceil \frac{\text{Blocks}}{100} \times 3.3 \right\rceilA standard 8x8x16 block with a 3/8" mortar joint covers 0.8889 sq ft (1.125 blocks per sq ft). Approximately 3.3 seventy-pound mortar bags are needed per 100 blocks.
Scenario: Building a 30 ft long by 6 ft high retaining wall with reinforced grouted cores every 32" OC.
Wall area: 30 × 6 = 180 sq ft.
Blocks required: 180 × 1.125 = 202.5 blocks (+ 5% waste = 213 blocks).
Mortar: (213 ÷ 100) × 3.3 = 7.02 -> 8 bags of 70-lb Type S mortar.
Core fill grout: ~0.89 cubic yards.
There are 1.125 standard 8"×8"×16" concrete blocks in one square foot of wall surface area.
An 8 ft high by 10 ft long wall is 80 square feet. 80 × 1.125 = 90 blocks (+ 5% cuts = 95 blocks).
You need approximately 3 to 3.5 bags (70-lb or 80-lb bags) of Type S or Type N masonry mortar per 100 blocks.
The actual dimensions are 7-5/8" high × 7-5/8" deep × 15-5/8" long. When laid with a standard 3/8-inch mortar joint, the nominal dimension is exactly 8" × 8" × 16".
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