Retaining Wall Calculator

Calculate blocks, gravel fill and anchor rows needed for any retaining wall.

Blocks per Course
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Number of Courses
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Total Blocks
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Gravel Fill (cubic yards)
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Deadman / Anchor Rows
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How the Retaining Wall Calculator Works

This retaining wall calculator determines block count by dividing the wall length (in inches) by the block width to get blocks per course, and dividing the wall height (in inches) by the block height to get the number of courses. Total blocks is courses times blocks per course. Gravel fill volume is estimated using a base width of half the wall height — a common structural rule of thumb — multiplied by wall height and wall length, then converted from cubic feet to cubic yards. For walls taller than 3 feet, deadman anchors (tie-back courses set into the hillside) are recommended every 4 courses to resist soil pressure. Always consult a structural engineer for walls over 4 feet.

Frequently Asked Questions

How many retaining wall blocks do I need?
Multiply blocks per course (wall length ÷ block length) by the number of courses (wall height ÷ block height). Add 5–10% waste.
How deep should a retaining wall base be?
For every foot of wall height, the base should extend back at least 6 inches. A 3-ft wall needs an 18-inch compacted gravel base.
Do retaining walls need drainage?
Yes. Install a perforated drain pipe at the base and backfill with ¾-inch crushed gravel to prevent hydrostatic pressure buildup.
How tall can a retaining wall be without engineering?
Most municipalities allow retaining walls up to 3–4 feet without a structural engineer's approval. Taller walls require permits.

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