Retaining Wall Calculator

A retaining wall is a structure built to hold back soil on a slope or elevation change — and estimating materials before you build saves time and money. Enter your wall width, wall height, block dimensions, and cap block width into the Retaining Wall Calculator to get the total standard blocks needed, cap blocks, base gravel, and backfill gravel. Add optional prices for block price, cap block price, base gravel, and backfill gravel to see your estimated total cost.

ft

Total length of the wall

ft

Height of the wall from base to top

in

Width of each standard block

in

Height of each standard block

Price per standard block (optional)

in

Width of cap blocks for top row

Price per cap block (optional)

/cubic yard

Price per cubic yard of base gravel

/cubic yard

Price per cubic yard of backfill gravel

Results

Total Standard Blocks Needed

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Cap Blocks Needed

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Base Gravel

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Backfill Gravel

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Estimated Total Cost

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Frequently Asked Questions

How do I calculate the number of blocks I need for a retaining wall?

Calculate the number of rows by dividing wall height by block height, and the number of columns by dividing wall width by block width. Multiply rows by columns to get the total number of blocks needed.

What is the purpose of backfill in a retaining wall?

Backfill gravel provides proper drainage behind the retaining wall, preventing water buildup that could cause pressure and potential wall failure. It should extend from the base to about 6 inches below the top of the wall.

How much base gravel do I need for my retaining wall?

Base gravel should be 6 inches deep and extend 6 inches beyond both sides of the wall. Calculate the volume as: (wall width + 1 foot) × 0.5 feet × wall depth, then convert to cubic yards.

Do I need cap blocks for my retaining wall?

Cap blocks are recommended for the top row as they provide a finished appearance and better structural integrity. They're typically wider than standard blocks and help distribute weight evenly.

How deep should my retaining wall foundation be?

The foundation depth should be approximately 10% of the wall height, with a minimum of 6 inches. For taller walls over 4 feet, consider consulting a structural engineer for proper foundation requirements.

What factors affect retaining wall construction costs?

Main cost factors include block type and quality, wall height and length, site preparation requirements, drainage needs, and local labor costs. Additional features like lighting or curves will increase costs.

Can I build a retaining wall myself or do I need a contractor?

Walls under 4 feet high can often be DIY projects with proper planning and materials. Taller walls or those holding back significant soil loads should be designed and built by professionals to ensure safety and compliance with local codes.