Concrete Retaining Wall Calculator

Calculator built by BuilderToolkits | Updated February 2026

Estimate concrete for retaining walls using length, height, wall thickness, and waste. This retaining wall calculator returns cubic yards, cubic feet, and 80‑lb bag counts, and includes an optional footing thickness so you can add a base pour when needed. For slab takeoffs, start with the Concrete Slab Calculator. For reinforcement and subbase planning, also use the rebar estimator and the gravel base calculator.

Inputs

Typical poured walls range from 6–10 inches depending on height and loads.

Footing volume uses the wall thickness as footing width.

Drainage and gravel backfill reduce hydrostatic pressure. Plan for a drain tile and free-draining gravel behind the wall.

Results

Concrete volume
2.17 yd³
58.67 ft³ total
Includes wall + footing and 10% waste.
80-lb bags (rough)
98 bags
Assumes ~0.6 ft³ yield per 80-lb bag (varies by mix).

Assumptions

  • Wall is a straight, uniform thickness section.
  • Footing volume assumes footing width equals wall thickness.
  • Waste accounts for spillage, form variation, and over-excavation.

Next Steps

✓Round up to the nearest 0.25 yd³ for ready-mix orders.
✓Plan drainage and backfill volume; the gravel base calculator helps estimate backfill.
✓Size reinforcement with the rebar estimator.

Example

A 20 ft × 4 ft wall at 8 in thickness with 10% waste needs about 2.17 yd³ of concrete.

How to Calculate Retaining Wall Concrete (Formula)

Wall volume (ft³): Length (ft) × Height (ft) × Thickness (ft)

Footing volume (ft³): Length (ft) × Wall thickness (ft) × Footing thickness (ft)

Total concrete (yd³): (Wall + Footing volume) ÷ 27 × (1 + Waste %)

FAQ

How thick should a retaining wall be?

Many residential retaining walls are 6–10 inches thick, but thickness depends on wall height, soil loads, and design. For bagged mixes, use the concrete bag calculator to convert volume to bags.

Do I need rebar?

Most poured concrete retaining walls need reinforcement. Use the rebar estimator to plan quantities, then confirm spacing and bar size with local code or a structural engineer.

Do I need drainage?

Yes. Drainage and gravel backfill reduce hydrostatic pressure. Use a drain tile and free-draining gravel behind the wall whenever possible—see the gravel base calculator for backfill volume.

How deep should footings be?

Footing depth depends on soil and frost depth. Many retaining walls place footings below frost line, with depth set by local code or engineering.

How much gravel behind retaining wall?

A common approach is 12–18 inches of free-draining gravel directly behind the wall, plus a drain tile at the base. Adjust for wall height and site conditions.

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