Retaining Wall Block Calculator
Calculate the number of retaining wall blocks needed based on wall dimensions and block size.
Fill in the fields above and click Calculate.
Formula
Blocks per Row = Wall Length (ft) ÷ Block Length (ft)
Number of Rows = Wall Height (ft) ÷ Block Height (ft)
Base Blocks = Blocks per Row × Number of Rows
Total Blocks = ⌈ Base Blocks × (1 + Waste Factor / 100) ⌉
Block dimensions are converted from inches to feet before calculation (divide by 12).
Results are always rounded up to the nearest whole block.
Assumptions & References
- Wall is assumed to be a single-wythe (one block thick) straight wall.
- Block dimensions entered are face dimensions (length × height); depth/thickness is not required for block count.
- A standard retaining wall block is commonly 12 in × 6 in (face), but custom sizes are supported.
- A 10% waste factor is recommended to account for cuts, breakage, and irregular ends.
- This calculator does not account for batter (wall lean), stepped footings, or curved walls.
- Always consult a structural engineer for walls exceeding 4 ft in height or in areas with surcharge loads.
- Reference: Portland Cement Association (PCA) retaining wall design guidelines.