Poured-concrete retaining wall calculator

Estimate concrete for the wall and footing

Enter the wall run, wall height measured above the top of the footing and the thickness from your plans. A straight wall has one thickness. A linearly tapered wall uses the top and bottom thicknesses. Add a rectangular footing using its own length, width and thickness, or turn it off when that concrete is outside your estimate.

This calculator adds geometric concrete volumes and your chosen extra allowance. The initial dimensions are arithmetic examples, not recommended wall or footing sizes. Use the project’s design for geometry, reinforcement, concrete specification, drainage and approvals.

Keep the wall height above the footing

The upright wall, often called the stem, starts at the top face of the footing in this model. The full footing thickness is counted separately. If your drawing gives a height from the bottom of the footing to the wall top, subtract the footing thickness before entering wall height.

For example, a 5 ft overall height measured from the footing bottom and a 1 ft thick footing gives 4 ft of wall above the footing. Entering 5 ft of wall plus the full footing would count the stem-shaped overlap twice. Buried wall above the footing still belongs in the entered wall height; exposed height alone can undercount concrete.

Entered wall height = wall-top elevation − footing-top elevation
If a drawing gives overall height from footing bottom:
Entered wall height = overall height − footing thickness

Concrete volume formulas

Convert every dimension to a common length unit before multiplying. A linearly tapered cross-section has the average of its top and bottom thicknesses. That formula assumes the same cross-section along the whole run; it does not represent a wall whose height or thickness changes along its length.

Straight wall = wall run × wall height above footing × wall thickness
Tapered wall = wall run × wall height × (top thickness + bottom thickness) ÷ 2
Rectangular footing = footing length × footing width × footing thickness
Net concrete = wall volume + included footing volume
Extra volume = net concrete × extra allowance ÷ 100
Estimated order volume = net concrete + extra volume
Imperial: inches ÷ 12 = feet; cubic feet ÷ 27 = cubic yards
Metric: millimetres ÷ 1,000 = metres; 1 yd³ = 0.764554857984 m³

Worked example: 30 ft wall with a separate footing

A 30 ft run with 4 ft of wall above the footing and an 8 in constant thickness contains 30 × 4 × (8 ÷ 12) = 80 ft³. A separately entered 30 ft long × 24 in wide × 12 in thick footing contains 60 ft³. The combined net volume is 140 ft³, or about 5.185185 yd³.

An illustrative 10% allowance adds 14 ft³. The estimated order is 154 ft³, or about 5.703704 yd³ (4.360794 m³). Supplier order increments, minimum loads, separate pour schedules and any specified extra quantities need their own confirmation. The displayed numbers are rounded; calculations use full precision.

For an independent metric example, a 10 m run × 1.2 m wall × 200 mm thickness gives 2.4 m³. A 10 m × 600 mm × 300 mm footing gives 1.8 m³. The net is 4.2 m³, or 4.62 m³ with 10% extra. The metric fields use metres for lengths and wall height, and millimetres for wall thickness and footing width/thickness.

Set the extra allowance with the concrete supplier

NRMCA CIP 31 discusses ordering 4% to 10% beyond a plan-dimension estimate for contingencies. The calculator starts at 10% as an editable illustration. Confirm the actual allowance for the forms, placement and delivery arrangements rather than treating that entry as a guarantee.

NRMCA CIP 8 explains that fresh concrete is sold by volume and that yield is related to measured fresh density. Keep your measured geometry, purchasing allowance and the supplier’s delivery basis separate. The tool does not calculate a mix recipe, cement/sand/aggregate proportions or concrete mass.

What to add to the project takeoff separately

The volume estimate covers a straight run of solid concrete with a constant or linearly tapered cross-section, plus the optional rectangular footing. It makes no deductions for rebar, ducts or openings, and does not add shear keys, counterforts, returns, steps, blinding or excavation. Measure those separately and prevent overlaps when combining sections.

A calculated footing volume does not establish a safe footing size. Have the appropriate project professional specify soil and load requirements, sliding and overturning checks, reinforcement, concrete properties, joints, drainage, construction details and local approval requirements.