Retaining Wall Calculator
Enter your wall length, height, and block size to estimate the number of blocks, cap units, and base gravel needed for your retaining wall project.
What This Calculator Does
The retaining wall calculator estimates how many wall blocks, cap units, and how much gravel base material you need to build a straight segmental retaining wall, based on the wall’s overall length, height, and the dimensions of the block you plan to use.
How the Calculation Works
The number of courses (horizontal rows) is found by dividing the total wall height by the block height and rounding up. The number of blocks per course comes from dividing the wall length by the block length. Multiplying courses by blocks-per-course gives the total block count, and one extra row’s worth of units is estimated for the finishing cap row. A compacted gravel base is standard beneath and slightly behind most retaining walls, so the calculator also estimates that base material volume in cubic yards.
Tips for Building a Retaining Wall
- Walls taller than about 3 to 4 feet often require engineering, geogrid reinforcement, and permits — check your local building department before starting.
- Always compact a gravel base and set the first course below grade for stability.
- Add 5 to 10 percent extra blocks to account for cuts, corners, and curves in the wall layout.
Note: This tool provides general estimates for planning and educational purposes only. Consult a structural engineer or licensed contractor for taller walls or wherever soil conditions and drainage may be a concern.