Retaining Wall Calculator
Calculate retaining wall blocks, base gravel, and capstones for any landscape wall.
Enter wall dimensions and block size to find total materials needed.
A segmental retaining wall is built from interlocking concrete blocks stacked without mortar. The number of blocks depends on the wall’s face area divided by each block’s face area.
Total face area = Wall length × Wall height Blocks per course = Wall length / Block length Number of courses = Wall height / Block height Total blocks = Blocks per course × Number of courses
Always add 5-10% for cuts, breakage, and adjustments at corners and ends.
Block dimensions vary by manufacturer, but common face sizes are 12" × 8", 16" × 6", and 8" × 6". For a 6-foot-tall wall, blocks need to be structural-grade (heavier, engineered for load). Decorative landscape blocks are typically suitable up to 3-4 feet.
The base course is buried in a trench:
- For walls under 3 feet: bury at least 6 inches (one full block height)
- For walls 3-6 feet: bury 1 inch per 1 foot of wall height
- The buried portion carries the wall’s lateral load into the ground
Base gravel (6-inch compacted layer beneath the wall): Base gravel volume ≈ Wall length × 1 ft × 0.5 ft = 0.5 × length cubic feet
Capstones are the decorative flat blocks on the top row. One capstone per linear foot of wall is a common estimate for 12-inch cap blocks.
For walls over 4 feet, consult a landscape engineer. Deadman anchors or geogrid reinforcement may be required for taller walls to resist the lateral pressure of soil behind them.