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Retaining Wall Calculator
Enter the wall length and height. This returns the block count by course, the base trench, and the drainage stone behind it — the part that fails when it is skipped.
Your numbers
Result
Blocks needed
189
blocks
- CoursesIncluding buried base
- 6courses
- Blocks per course
- 30blocks
- Cap blocks
- 30blocks
- Base gravel
- 0.65cubic yards
- Drainage stone behind wall
- 4.44cubic yards
- Geogrid layers0 = not required at this height
- 0layers
- Total wall height
- 4ft
How this is calculated
- Courses = exposed height in inches ÷ block height, plus buried base courses.
- Blocks per course = wall length in inches ÷ block face length.
- Drainage stone = a 12 in wide column of clean stone the full height behind the wall.
Before you order
- Almost every retaining wall failure is water, not weight. Clean drainage stone and a perforated drain pipe at the base are what keep hydrostatic pressure from pushing the wall over.
- Over about 4 ft, most jurisdictions require an engineered design and a permit, and geogrid reinforcement into the slope behind. Do not treat a tall wall as a bigger version of a short one.
- The base course does the work. It goes on compacted gravel, buried, and dead level — every error in it is multiplied by every course above.
- A wall holding up a driveway or a structure is a surcharge load and always needs engineering.
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