Retaining Wall Concrete Calculator: Stem and Footing
A poured retaining wall 20 ft long with a 4 ft stem 8 in thick on a 2×1 ft footing needs 3.80 cubic yards of concrete with 10% extra.
Advanced options: waste, prices
NRMCA advises ordering 4 to 10 percent over the estimate.
Concrete needed (with 10% extra)
3.80 yd³
2.91 m³ · 93.33 ft³ before extra
Retaining wall: 20 ft × 4 ft × 8 in × 2 ft × 1 ft. Over about 1 yd³: order ready-mix.
Premix bags
- 80 lb172
- 60 lb229
- 50 lb274
- 40 lb343
- Ready-mix cost
- $608
- Weight
- 14,000 lb
Full breakdown
| Volume before extra | 3.46 yd³ · 2.64 m³ |
|---|---|
| With 10% extra | 3.80 yd³ |
| Weight (150 lb/ft³) | 14,000 lb · 7 tons |
| Pallets of 40 lb (80 bags each) | 5 |
| Pallets of 60 lb (56 bags each) | 5 |
| Pallets of 80 lb (42 bags each) | 5 |
| Truckloads at 12 yd³ | 1 |
| Truckloads at 8 yd³ | 1 |
Bag counts round up, as Quikrete's own calculator does. Cost uses your prices; delivery and short-load fees are extra.
Key takeaways
- Concrete = stem volume + footing volume.
- A 20 ft wall, 4 ft stem, 8 in thick, 2×1 ft footing = 3.80 yd³ with extra.
- Over 48 in of unbalanced fill needs an engineer (IRC R404.4).
- Block retaining walls: use the block calculator.
How Much Concrete for a Retaining Wall?
You need the stem volume plus the footing volume. A 20 ft wall with a 4 ft stem 8 in thick holds 53.33 ft³ in the stem and 40 ft³ in a 2×1 ft footing, 93.33 ft³ in total, which is 3.80 yd³ with 10% extra.
Retaining Wall Concrete Formula
ft³ = L × stem height × (stem thickness (in) ÷ 12) + L × footing width × footing depthRetaining Wall Concrete by Height
| Stem height (20 ft wall, 8 in stem, 2×1 ft footing) | ft³ | yd³ with 10% |
|---|---|---|
| 2 ft | 66.67 | 2.72 |
| 3 ft | 80 | 3.26 |
| 4 ft | 93.33 | 3.80 |
Taller walls need wider footings and reinforcement from an engineer's design.
When Does a Retaining Wall Need an Engineer?
A retaining wall needs engineered design under the 2021 IRC when it is not supported at the top and retains more than 48 in (1,219 mm) of unbalanced fill, or when it exceeds 24 in (610 mm) and resists other lateral loads, such as a driveway surcharge (R404.4).
Poured vs Block Retaining Wall
A poured wall needs forms and a truck or many bags; a block wall uses units stacked on a footing. Count blocks with the block calculator.
Worked Examples: Three Retaining Walls
Garden wall, 30 ft, 2 ft stem 8 in thick, 1.5×1 ft footing. 85 ft³; with extra, 3.46 yd³.
Driveway wall, 50 ft, 3 ft stem 10 in thick, 2.5×1 ft footing. 250 ft³; with extra, 10.19 yd³.
Yard wall, 20 ft, 4 ft stem 8 in thick, 2×1 ft footing. 93.33 ft³; with extra, 3.80 yd³ (at the 48 in limit, check with an engineer).
Retaining Wall Footing Size
The footing spreads the wall's load and resists sliding; the IRC footing minimum is 12 in wide and 6 in deep (R403.1.1), but retaining walls over the R404.4 limits need an engineered footing size.
Drainage Behind a Retaining Wall
Water pressure behind a wall adds load; the IRC asks that retaining walls be designed against overturning, sliding and water uplift where engineering is required (R404.4), so plan drainage with the design.
Retaining Wall Concrete in Cubic Meters
In metric, a 6 m wall with a 1.2 m stem 20 cm thick on a 60×30 cm footing holds 1.44 + 1.08 = 2.52 m³ before extra; switch the calculator to Metric to enter meters.
Retaining Wall Forms and Pouring
A poured retaining wall needs a footing form, then wall forms braced against the concrete's pressure; pour the footing first or both together as your design shows, and keep the pour continuous with ready-mix to avoid cold joints. Order the full volume plus 4 to 10 percent (NRMCA).
Retaining Wall Concrete Calculator FAQ
How much concrete for retaining wall posts?
Size each post footing as a round pier with the deck pier calculator or the concrete tube calculator.
How much does a concrete retaining wall cost?
Concrete for the default 20 ft wall costs $608–$741 at $160–195 per yard; forms, steel and labor are extra.
How much concrete for a block retaining wall?
Only the footing and core fill use concrete; size the footing with the footing calculator and count blocks with the concrete block calculator.
Next step
Check the height against IRC R404.4, then compare with a block wall on the concrete block calculator.
Official sources
Last reviewed 2026-11-05. Numbers come from our tested engine; see how we calculate and our sources.