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 the unit selector (m, cm, mm), then configure materials and drainage. The calculator returns course count, material quantities, gravel backfill tonnage, drain pipe, filter fabric, geogrid, and an itemized cost estimate in your chosen currency.
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)
Segmental retaining wall coursing follows Eurocode 6 and EN 1992-1-1 for the concrete option. Course count is wall height ÷ block height, rounded up; blocks per course is wall length ÷ block length, rounded up, then a waste factor (5% for blocks, 10% for cut-heavy concrete and timber). A long straight run is slightly over-estimated because corner and cap units are billed as full blocks — order the nearest pallet quantity.
Block, concrete and timber walls
Standard blocks (300×100×200 mm, ~14 kg) suit gravity walls up to 1.2 m; large blocks (450×150×300 mm, ~30 kg) for taller runs. A 20 mm setback per course gives roughly 5–7° batter for sliding and overturning resistance. For mortared blockwork or grouted-cell stem walls instead of dry-stacked units, size the units with the block wall calculator and the mortar and grout with the mortar & grout calculator. Poured-concrete gravity stems use a tapered section (average of top and base thickness); detail and bar the section with the concrete beam & rebar calculator and price ready-mix or bagged mix with the concrete bag calculator.
Drainage and reinforcement
A 300 mm clean-stone chimney drain behind the wall, a 100 mm perforated pipe daylighted at the base, and a filter-fabric envelope relieve hydrostatic and frost pressure — the leading cause of SRW failure. Gravel is taken at ≈1.6 tonnes/m³. Geogrid is recommended on walls over 1.2 m; embedment length is the larger of 60% of wall height or 1.2 m. A clean stone face can also be dressed with the stone veneer calculator.
Formulas
Courses = ⌈H ÷ block height⌉ · Blocks = ⌈L ÷ block length⌉ × courses × (1 + waste). Concrete volume (m³) = L × H × ((t_top + t_base) ÷ 2) × (1 + waste). Gravel (t) = L × H × depth × 1.6. Geogrid rolls = ⌈layers × L × embedment ÷ 15⌉.
On install day
Three things estimators forget on segmental walls. Bury the first course — Eurocode 7 and NCMA SRW practice call for ~25 mm of embedment per 200 mm of exposed wall (a 1.2 m wall buries roughly 150 mm plus a 150 mm leveling-pad gravel layer), so order an extra row of blocks and don't count the buried course on your €/m² quote. Cap blocks and corners — caps are sold separately at €4–8 each in 2025 EU (vs. €2.50–4 for face blocks) and 90° corner units cost 20–30% more; for any wall over ~9 m, plan 2–3 spare caps for cut waste at returns. Pallet quantities — landscape blocks ship 60–110 per pallet at €300–800/pallet delivered; ordering 105% of net usually rounds to a full pallet, so buy by the pallet and use leftovers. Walls over 1.2 m or carrying a vehicle / pool surcharge need a stamped Eurocode 7 design with geogrid — this calculator's geogrid quantity is a takeoff aid, not the engineer's layout.
FAQ
How tall can I build without engineering? Most European jurisdictions allow gravity walls up to 1.2 m without a stamped design. Taller, tiered, or surcharged walls typically require geogrid reinforcement and structural calculations per Eurocode 7.
How much gravel do I need behind a retaining wall? Standard practice is a 300 mm clean crushed-stone zone behind the wall over the full height. This calculator converts that volume to tonnes at ≈1.6 t/m³.
