Free concrete calculator
Concrete Retaining Wall Calculator
Estimate the concrete volume and ready-mix cost for a poured retaining wall.
- Wall face area
- 200 sq ft
- Concrete with 10% waste
- 5.4 cu yd
- Ready-mix material
- $742
- Wall footprint
- 33 sq ft
Concrete Retaining Wall Estimating Notes
- Retaining walls hold back soil, so drainage matters as much as concrete. A wall with nowhere for water to go fails from hydrostatic pressure long before it fails from load.
- Calculate the footing separately. A poured wall footing is typically about twice the wall thickness wide and set below the frost line.
- Walls retaining more than about 4 ft of soil generally need an engineered design and a permit.
- Run a perforated drain pipe behind the base in free-draining gravel, and add weep holes so trapped water can escape.
- 8 inches is the usual minimum thickness for a poured residential wall. 6 inches only works on short garden walls.
- Add 10% waste. Wall forms bulge slightly under a full pour and you lose volume at the top edge.
Concrete Retaining Wall Calculator FAQs
How much concrete does a retaining wall need?
Multiply length by height by thickness in feet, then divide by 27 for cubic yards. A 50 ft wall 4 ft tall and 8 inches thick comes to about 4.9 cubic yards before waste. Work out the footing volume separately and add it.
How thick should a concrete retaining wall be?
8 inches is the common residential minimum for a poured wall up to roughly 4 ft of retained height. Taller walls typically step up to 10 or 12 inches with engineered reinforcement.
Does a retaining wall need a footing?
Yes, for poured concrete. The footing spreads the load into the soil and resists overturning. It is usually about twice the wall thickness wide and placed below the local frost line.
How much rebar does a retaining wall need?
A typical residential wall uses vertical #4 bar at 12 to 18 inches on centre, doweled into the footing, with horizontal bar every 12 to 16 inches. Exact spacing should come from an engineered design on anything tall.
Is poured concrete or block cheaper for a retaining wall?
Block is often cheaper on materials and needs no formwork. Poured concrete is stronger at the same thickness and faster on long straight runs. Local labour rates and wall length usually decide which comes out ahead.
Do I need a permit for a retaining wall?
Most jurisdictions require one above about 4 ft of retained height, and some require one at any height if the wall sits near a property line, structure, or slope. Check locally before you pour.