Retaining Wall Calculator
Estimate the blocks and caps for a segmental retaining wall or garden wall. Enter the wall size and block dimensions to get the number of courses, blocks and cap stones.
- Cap blocks
- 15 caps
- Courses (rows)
- 7 (incl. 1 buried)
- Blocks per course
- 15
- Wall face area
- 60 sq ft
How this calculator works
The number of courses (rows) is the wall height divided by the block height, rounded up. Most installers bury the first course below ground, which adds one more row.
Blocks per course are the wall length divided by the block face length. Total blocks are courses × blocks per course, plus extra for cuts and breakage.
Cap stones run along the top of the wall, so they depend only on the length of the wall and the cap length.
Example: a 20 ft long, 3 ft high wall with 16 × 6 in blocks
- Courses: 36 in ÷ 6 in = 6, plus 1 buried course = 7.
- Blocks per course: 240 in ÷ 16 in = 15.
- Blocks: 7 × 15 = 105, plus 5% = 111 blocks.
- Caps: 240 in ÷ 16 in = 15 caps.
Quick reference
| Wall height | Courses | Blocks |
|---|---|---|
| 1 ft | 3 | 48 |
| 2 ft | 5 | 79 |
| 3 ft | 7 | 111 |
| 4 ft | 9 | 142 |
Tips before you buy
- Walls taller than about 4 feet usually require engineering, geogrid reinforcement and a permit.
- Set the first course on a compacted gravel leveling pad about 6 inches deep, and backfill behind the wall with clean gravel for drainage.
- Block sizes vary by brand; enter the face dimensions printed on the product.
Frequently asked questions
How many retaining wall blocks do I need?
Divide the wall length by the block length to get blocks per row, and the wall height by the block height to get rows (add one buried row). Multiply the two and add 5% extra.
Should the first row of a retaining wall be buried?
Yes. Burying the first course — typically about 10% of the wall height, with a minimum of a few inches — stops the base from sliding and is recommended by most block manufacturers.
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Last updated October 25, 2026