Retaining Wall Calculator
How many blocks do you need? Enter your wall size and block size.
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Courses (rows) high—
Blocks per course—
Estimated cost—
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How this calculator works
It works out how many blocks fit in one row along the wall, how many rows tall the wall is, and multiplies the two for the total block count.
Worked example — a 20 ft long, 3 ft high wall with 12 × 4 in blocks:
20 blocks per row × 9 rows = 180 blocks.
Plan a buried base course
The bottom row of a retaining wall should sit below grade on a compacted gravel base. Include that buried course in your height when ordering.
Frequently asked questions
How many blocks for a retaining wall?
Multiply blocks-per-row by the number of rows — about 180 blocks for a 20 ft × 3 ft wall with standard blocks.
How tall can a DIY retaining wall be?
Walls over about 3–4 feet usually need engineering and permits — check local rules.
Planning an outdoor project
Outdoor quantities vary with site shape, access, drainage, soil conditions, and local material availability. Break irregular areas into simple sections, confirm the product specification with your supplier, and check permits or utility requirements before starting work.
How to use this estimate
- Measure the project in the units shown and recheck your measurements before ordering.
- Use the waste allowance as a planning buffer, not as a substitute for a detailed material takeoff.
- Compare the result with the package yield, coverage, or weight listed by your supplier.
- Prices are user-entered estimates and may change by location, product, delivery, and season.
Accuracy and limitations
Calculapedia provides educational planning estimates. It does not inspect your site, select products, guarantee quantities, or replace a contractor, engineer, architect, building official, or supplier. Confirm the final quantity and any safety or code requirements before buying or building.