Retaining Wall Block Calculator
Enter the wall size and the block size.
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Retaining Wall Block Calculator by TheCalcTools
How the Retaining Wall Block Calculator works
Blocks per course = wall length ÷ block length; courses = wall height ÷ block height, plus any buried below grade. Most manufacturers recommend burying the first course for stability.
Walls over about 3 to 4 feet, or holding back a slope or driveway, usually need engineering and a permit. Follow the block maker’s installation guide for drainage and geogrid.
The formula
Worked example
Using the default values shown in the calculator:
| Wall length (ft) | 30 |
|---|---|
| Wall height (ft) | 3 |
| Block length (in) | 12 |
| Block height (in) | 6 |
| Cap length (in, 0 for no caps) | 12 |
| Buried courses | 1 |
- A 30 ft wall 3 ft high with 12 × 6 in blocks: 30 blocks per course, 7 courses.
- Total 210 blocks and 30 caps.
Result:
| Blocks needed | 210 |
|---|---|
| Courses (rows) | 7 |
| Blocks per course | 30 |
| Cap stones | 30 |
Frequently asked questions
How tall can I build without an engineer?
It depends on local code; many places require engineering above about 4 feet, or less where there is a surcharge load.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.