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October 13, 2026

Retaining Wall Calculator

FREE LANDSCAPING CALCULATOR

Retaining Wall Calculator

Estimate retaining wall face area, blocks, backfill, drainage gravel, base material, and material costs. Enter your project measurements to generate a detailed estimate you can download.

1

Wall Measurements

Measurement system
Enter the exposed wall height for this material estimate.
Extra blocks for cuts, breakage, and spares.
2

Base, Backfill and Drainage

These dimensions provide rough material quantities only. Use your approved wall design and supplier recommendations for actual construction requirements.

Used to estimate the rectangular backfill volume.
Approximate thickness of the drainage gravel zone.
3

Optional Material Prices

Enter your local prices to estimate material costs. Example prices are editable and are not live supplier quotes.

4

Your Retaining Wall Estimate

Material estimate
Estimated wall blocks
—
Includes your extra-block allowance
Wall face area
—
Square feet
Total estimated gravel
—
Base and drainage gravel combined

Wall and Block Breakdown

MeasurementResult
Wall length—
Wall height—
Wall face area—
Wall face area in square meters—
Block face dimensions—
Face area per block—
Blocks before extra allowance—
Extra-block allowance—
Total blocks to order—

Backfill and Gravel Quantities

MaterialVolume before allowanceVolume with allowance
Backfill——
Drainage gravel zone——
Base gravel——
Combined gravel estimate——

Estimated Material Costs

MaterialEstimated quantityEstimated cost
Wall blocks——
Backfill material——
Drainage and base gravel——
Estimated total material cost——
Important: These are preliminary quantity estimates, not a retaining-wall design. The calculator does not evaluate soil pressure, surcharge loads, sliding, overturning, bearing capacity, reinforcement, footing design, or drainage performance. Tall walls, sloping sites, vehicle loads, weak soils, and walls near buildings may require a qualified engineer and local permits.

Download Your Results

Download a text report containing the entered measurements, block count, estimated material volumes, and cost breakdown only.

How to Calculate Retaining Wall Materials

Estimate the wall face area first, then divide it by the face area of one block. Backfill and gravel quantities are calculated separately using their approximate placement dimensions.

Wall face area
Wall length × wall height
Blocks before extra allowance
Wall face area ÷ block face area
Blocks to order
Round up the base block count after adding the selected extra percentage.
Rectangular material volume
Length × depth × height
Cubic yards
Cubic feet ÷ 27

Example Retaining Wall Estimate

For a wall that is 30 feet long and 3 feet high, the face area is 90 square feet. If the block face is 16 inches long by 6 inches high, each block covers approximately 0.667 square feet of face area.

  • Wall face area: 30 × 3 = 90 square feet.
  • Block face area: (16 ÷ 12) × (6 ÷ 12) ≈ 0.667 square feet.
  • Base block count: 90 ÷ 0.667 ≈ 135 blocks.
  • With a 10% extra allowance: approximately 149 blocks.

This example estimates face coverage only. Actual block quantities may differ due to corner units, caps, setbacks, interlocking geometry, buried courses, cuts, and manufacturer instructions.

Frequently Asked Questions

How many blocks do I need for a retaining wall?

Divide the wall’s face area by the face area of one block, then allow for cuts and waste. Check the block manufacturer’s coverage information for the most accurate estimate.

Does the calculator include cap blocks?

No. Cap blocks are not included because cap dimensions and layout vary by product. Estimate them separately using the wall length and the cap manufacturer’s coverage.

How much drainage gravel is needed?

The calculator estimates a rectangular gravel zone from your entered wall length, height, and gravel depth. Actual drainage systems depend on wall design, soil, drainage outlets, and manufacturer specifications.

Is this calculator suitable for tall retaining walls?

It estimates materials only and does not determine whether a wall is structurally safe. A qualified professional may be required depending on height, soil, loads, and local regulations.

Are labor and delivery included in the price?

No. The cost estimate uses the material prices you enter. Labor, delivery, taxes, equipment, excavation, geogrid, drainage pipe, caps, and other accessories are excluded.