Retaining Wall Calculator — m, blocks, cost
How to use this calculator
Select wall type (landscape blocks, poured concrete, or timber ties), enter wall length and height with unit selector (m, cm, mm), then configure materials and drainage. Results update instantly with material quantities, courses, drainage requirements, and cost.
Blocks — choose standard (300×100×200 mm) or large (450×150×300 mm) landscape blocks with setback per course.
Concrete — tapered gravity wall with top/base thickness and optional rebar.
Timber — 150×150 or 150×200 mm ties with deadman anchors.
Drainage — gravel backfill, drain pipe, filter fabric, and geogrid for walls over 1.2 m.
Saved Calculations
| Time | Type | L×H | Material | Gravel | Cost |
|---|
How to Calculate Materials for a Retaining Wall (Metric)
This retaining wall calculator estimates materials for three wall types: landscape/segmental blocks, poured concrete (gravity), and timber ties. Enter wall length and height in metres, centimetres, or millimetres, select block size or concrete thickness, and configure drainage. Results include block count (with courses), concrete volume in m³, or timber count, plus gravel backfill tonnage, drain pipe, filter fabric, and geogrid requirements.
Landscape Block Walls
Standard blocks (300×100×200 mm, ~14 kg) for walls up to 1.2 m. Large blocks (450×150×300 mm, ~30 kg) for taller walls. Setback of 20 mm per course provides batter for stability. Walls over 1.2 m require geogrid reinforcement.
Drainage Requirements
Proper drainage is critical. A 300 mm gravel backfill behind the wall with a 100 mm perforated drain pipe at the base and filter fabric prevents hydrostatic pressure buildup. Gravel density: approximately 1.6 tonnes per m³.
FAQ
How tall can I build without engineering? Most European jurisdictions allow gravity walls up to 1.2 m without engineering. Walls above this typically require geogrid reinforcement and structural calculations per Eurocode 7.
How much gravel do I need behind a retaining wall? Standard practice is 300 mm of clean crushed gravel behind the wall, extending the full height. This calculator computes the exact tonnage.
