Retaining Wall Calculator

Overview

Estimates modular wall blocks from wall face area and adds base, backfill, drainage stone, fabric, cap blocks, and geogrid planning quantities.

Assumptions

• Wall dimensions are straight and uniform.
• Block dimensions and fixed allowances in the calculator determine course and material counts.

Worked example

A 20-ft by 3-ft wall has 60 sq ft of face. With 12 × 4 in blocks (0.333 sq ft), the block calculation is ceil(60 ÷ 0.333 × 1.10) = 199.

Common mistakes

• Measuring visible height but not buried base course.
• Using a block count as a wall engineering plan.

Limitations

Slopes, surcharges, water, soil pressure, corners, and geogrid design are not evaluated.

Safety and local requirements

Excavation can expose utilities and unstable soil. Local permits and engineered-wall thresholds vary—check before building.

Sources

• International Code Council — code reference background
• OSHA — Landscaping and Horticulture