The Retaining Wall Block & Backfill Sizer calculates material takeoffs for segmental concrete terrace and garden retaining walls.

### Wall Geometry & Material Calculations - Visible and Buried Courses: Structural guidelines require burying at least one base course below grade to prevent toe kickout ($$\text{Visible Courses} = \lceil(\text{Wall Height (ft)} \times 12) / \text{Block Height (in)}\rceil$$, $$\text{Total Courses} = \text{Visible} + 1$$). - Blocks Per Course & Cutting Waste: Units per row equal $$\lceil(\text{Wall Length (ft)} \times 12) / \text{Block Length (in)}\rceil$$. Total blocks include a 5% contingency multiplier ($$\times 1.05$$) for end cuts and corner splits. - Capstones: Finished walls require a continuous top cap row matching the wall length. - Crushed Stone Drainage Backfill: Proper hydrostatic pressure relief requires a minimum 12-inch gravel chimney directly behind the wall ($$\text{Gravel (cu yds)} = (\text{Length} \times \text{Height} \times 1.0) / 27$$).

### Worked Numeric Example - Wall Dimensions: 32 feet long × 3 feet exposed height - Block Dimensions: Standard 16" length × 6" height - Calculation: - Visible courses: $(3 \times 12) / 6 = 6$ courses - Total courses with buried base: $6 + 1 = 7$ courses - Blocks per row: $(32 \times 12) / 16 = 24$ blocks - Base block count: $24 \times 7 = 168$ blocks - Total with 5% waste: $\lceil 168 \times 1.05 \rceil = 177$ blocks - Capstones needed: 24 caps - Drainage gravel volume: $(32 \times 3 \times 1) / 27 = 3.56\text{ cu yds}$ (~1.2 cu yds for nominal 1-foot backfill depth)

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