Free Tool
Free retaining wall calculator
Enter your wall length and height to get the wall blocks, courses, cap blocks, and base gravel. Free, no signup.
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Count it by the course
A block retaining wall is counted by courses, the rows stacked from the base to the top. Enter the wall length and height and your block size, and the calculator gives you the blocks, the courses, the cap, and the gravel under it.
Courses are the height divided by the block height, and each course holds enough blocks to run the length. The calculator rounds both up, since a partial course still needs a full row and a partial block still gets bought.
Cap blocks finish the top and are usually a different piece, glued down, so they are ordered on their own line. The base is a compacted gravel footing under the first course, figured here about a foot wide and 6 inches deep, and getting it flat and solid is what keeps the wall straight for years.
Height is where judgment comes in. A short garden wall is a weekend project, but a wall over about 3 to 4 feet holds real load and usually needs engineering, geogrid reinforcement, and drainage behind it. Check your local code before you build tall, since many require a permit and a stamped design above a set height.
Retaining Wall Calculator questions
How many blocks for a retaining wall?
Courses times the blocks per course. The calculator figures both from your wall size and block size, then rounds up.
Do I need cap blocks?
Most segmental walls finish with a cap course, glued on top. The calculator counts them separately since they are a different block.
When does a retaining wall need engineering?
Often above about 3 to 4 feet, where the load is real. Check your local code, since many require a permit and a stamped design above a set height.
Is this really free?
Yes. No email, no signup, and nothing you type leaves your browser.
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Disclaimer: These free tools and templates are provided for general information and estimating purposes only. All results — including quantities, material and cost estimates, load, sizing, and span figures, scores, and any guidance or warnings — are rough approximations that may not fit your specific project, site conditions, local building codes, or current prices. They are not engineering, architectural, structural, legal, financial, or other professional advice, and are not a substitute for a licensed engineer, architect, contractor, or other qualified professional. Always confirm quantities, sizing, and structural, electrical, mechanical, and code requirements with a licensed professional and your local authority having jurisdiction before purchasing materials or performing any work. Werx makes no warranty as to accuracy and accepts no liability for any decision made using these tools. Use at your own risk. See our Terms of Service.