How this calculator works
It works out how many blocks fit in one row along the wall, how many rows tall the wall is, and multiplies the two for the total block count.
Worked example — a 20 ft long, 3 ft high wall with 12 × 4 in blocks:
20 blocks per row × 9 rows = 180 blocks.
20 blocks per row × 9 rows = 180 blocks.
Plan a buried base course
The bottom row of a retaining wall should sit below grade on a compacted gravel base. Include that buried course in your height when ordering.
Frequently asked questions
How many blocks for a retaining wall?
Multiply blocks-per-row by the number of rows — about 180 blocks for a 20 ft × 3 ft wall with standard blocks.
How tall can a DIY retaining wall be?
Walls over about 3–4 feet usually need engineering and permits — check local rules.