Retaining Wall Calculator
Count blocks for a segmental retaining wall.
Enter your wall length and height plus your block dimensions to get the number of retaining-wall blocks and courses. Works for segmental block, garden walls, and raised-bed borders.
How it works
Blocks per course is the wall length divided by the block length. Courses is the wall height divided by the block height. Multiply the two for total blocks. For walls over about 3–4 feet, check local code — taller walls often need engineering, geogrid, or a permit.
Frequently asked questions
How many blocks for a retaining wall?
Divide wall length by block length for blocks per course, divide wall height by block height for courses, and multiply. A 20-ft, 3-ft-tall wall with 12×4-inch blocks needs about 180 blocks.
How tall can a retaining wall be without engineering?
Many areas allow up to about 3–4 feet before requiring engineering or a permit. Always confirm with your local building department.
Do I need a base course below grade?
Yes — bury the first course about one block-height below grade on a compacted gravel base for stability. Include it in your count.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.