Retaining Wall Block Calculator
A 20-foot-long, 2-foot-high wall built from 6 × 16 inch blocks needs about 60 blocks plus 15 caps.
Block counts come from the wall face area divided by the face area of one block. Enter the finished length and height — the calculator also returns the number of courses.
Retaining wall block calculator
You need
0blocks
- Wall face area
- 0 sq ft
- Including waste
- 0 sq ft
- Estimated cost
- $0
Face dimensions follow the most common segmental wall block sizes sold in the US. Estimates only — confirm with your supplier before ordering.
Retaining wall block coverage by option
| Option | Covers | Per 500 sq ft |
|---|---|---|
| 6" H × 16" W (0.67 sq ft face) | 0.67 sq ft | 750 blocks |
| 4" H × 12" W (0.33 sq ft face) | 0.33 sq ft | 1502 blocks |
| 8" H × 18" W (1.00 sq ft face) | 1 sq ft | 500 blocks |
Retaining wall block questions people actually ask
- How many retaining wall blocks do I need?
- Divide the wall face area (length × height) by the face area of one block. A 6 × 16 inch block covers 0.67 square feet, so 100 square feet of wall takes about 150 blocks.
- How deep should the base course be?
- Bury the first course so the top sits at or just below grade, over 6 inches of compacted gravel. That means digging roughly one block height plus 6 inches.
- How high can I build without an engineer?
- Most jurisdictions allow up to 3 or 4 feet for an unreinforced segmental wall. Anything taller, or holding back a slope or driveway, needs engineering and often a permit — check locally.
Gear for a retaining wall block job
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How this number is calculated
Face dimensions follow the most common segmental wall block sizes sold in the US. Counts are the total area divided by the coverage of one unit, rounded up, with your waste allowance applied. See all our assumptions.