How the calculation works
Courses = round up (wall height ÷ unit course height). Units per course = round up (wall length ÷ unit length). Add the selected purchase allowance.
A worked example
A 20 ft long face with 16 in modules needs 15 units per course. A 3 ft total height with 6 in courses has 6 courses: 90 units before allowance.
What to check before using the result
- Straight-face material count only. Curves, caps, corners, drainage and reinforcement are separate.
- This is not a retaining-wall stability or height-approval tool.
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References & product information
Method prepared 2026-10-21. See our calculation and editorial methods. Spotted a problem? Tell us about it.