How deep should the footing be for a retaining wall?

A common rule of thumb is to bury one block (8 inches) below grade for every 3 courses above ground, with a minimum of one course buried. The calculator applies a 10% height addition to account for below-grade courses and footing depth.

What size block does this calculator assume?

The default is a standard 8 in × 8 in × 16 in concrete masonry unit (CMU). You can change the dimensions to match the actual blocks you plan to use.

Does the calculator include mortar?

The block count includes a 10% waste allowance that covers mortar joints, cuts, and breakage. For precise mortar volume, use the Mortar Calculator.

What gravel base depth is recommended?

A compacted gravel base of at least 6 inches (15 cm) is standard. The calculator uses 6 inches as its base depth, which you can adjust for your local code requirements.

What rebar schedule does this use?

The calculator assumes vertical #4 rebar every 4 feet (1.2 m) along the wall length, plus one horizontal bar every 2 courses. This matches typical residential retaining wall specs; consult a structural engineer for walls over 4 feet.

Should I hire an engineer for my retaining wall?

Most building codes require a licensed engineer to design retaining walls taller than 4 feet (1.2 m). Always check local regulations before construction.

Retaining Wall Calculator

Name: Retaining Wall Calculator
Availability: InStock
Author: Nham Vu

Estimate the blocks, concrete fill, gravel base, and rebar needed to build a retaining wall by entering its height and length.

Wall Dimensions

Wall Height (feet)

Wall Length (feet)

Block Dimensions

Height (in)

Width (in)

Length (in)

Materials Estimate

Enter dimensions and press Calculate

Summary

Estimate the blocks, concrete fill, gravel base, and rebar needed to build a retaining wall by entering its height and length.

How it works

Enter the wall height and total wall length.
Select your preferred unit system (imperial or metric).
Enter the block dimensions (defaults match a standard 8×8×16 in CMU block).
Click Calculate to generate a full materials estimate.
Review the block count, concrete fill volume, gravel base, and rebar schedule.

Use cases

Estimating materials for a garden retaining wall project.
Planning a driveway or slope retention wall.
Budgeting concrete block quantities before ordering.
Calculating gravel and rebar for a DIY landscape retaining wall.
Checking footing depth requirements based on wall height.
Comparing costs for different wall heights or lengths.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu