Retaining Wall Calculator — Blocks, Sleepers & Gabions

Our retaining wall calculator estimates the number of blocks, sleepers or gabion baskets needed based on your wall dimensions, plus the concrete required for the foundation.

Material calculations

• Concrete blocks (440 × 215 × 100mm): 10 per m² of wall face
• Railway sleepers (200 × 100 × 2400mm): Courses = height ÷ 0.2m, per course = length ÷ 2.4m
• Gabion baskets (1m L × 0.5m H × 1m D): Baskets high = height ÷ 0.5m, per row = length ÷ 1.0m

These counts are for a single-skin wall face — one block thick, one sleeper deep, or one basket deep. An earth-retaining wall normally needs a thicker section than a simple boundary wall: under BS 8002:2015 a gravity wall’s base is roughly one-third to one-half of the retained height, so double-skin blockwork, a wider sleeper section or a deeper gabion will need the count multiplied accordingly. Always follow the structural design for your wall.

Foundation calculation

Foundation volume = Wall length × Foundation width × 150mm depth

Concrete density: 2.4 tonnes per m³. Foundation width depends on the wall material (typically 300mm for blockwork and sleepers).

Important safety notes

• As a rule of thumb, any wall retaining more than about 1m–1.2m of soil should be designed by a structural engineer. All earth-retaining structures should be designed to BS 8002:2015 / BS EN 1997-1 (Eurocode 7) — there is no fixed statutory height trigger
• All retaining walls must have adequate drainage behind them
• Planning permission may be required depending on location and height
• Building Regulations may apply for walls retaining significant loads