Retaining Wall Block Calculator (Blocks, Caps, Base Gravel & Drainage Rock)
calc_retaining_wallHow many retaining wall blocks you need for a straight wall or a circle (fire pit, tree ring), including the buried course, cap units, base gravel for the leveling pad and drainage rock behind the wall. Block sizes are editable because every product line differs. Formula: Buried depth = max(exposed height ÷ bury ratio, minimum). Courses = ⌈(exposed height + buried depth − cap height) ÷ block height⌉. Blocks per course = ⌈run ÷ block face length⌉, where run = wall length, or π × outside diameter for a circle. Wall blocks = ⌈blocks per course × courses × (1 + waste%)⌉; caps = ⌈run ÷ cap length × (1 + waste%)⌉. Base gravel cu yd = run(ft) × trench width(in) × base depth(in) ÷ 144 ÷ 27; drainage rock cu yd = run(ft) × zone depth(in) × stacked block height(in) ÷ 144 ÷ 27 (straight walls only).
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| shape | No | Wall shape; default straight | |
| waste_pct | No | Block waste/cut allowance (%); default 5 | |
| min_bury_in | No | Minimum buried depth (from your block maker) (in); default 6 | |
| base_depth_in | No | Compacted base depth (in); default 6 | |
| bury_ratio_in | No | Bury 1 in of block for every __ in of exposed height (from your block maker) (in); default 8 | |
| cap_height_in | No | Cap height (0 = no caps) (in); default 0 | |
| cap_length_in | No | Cap face length (in); default 12 | |
| drain_zone_in | No | Drainage rock zone behind the block (in); default 12 | |
| block_height_in | No | Block height (from the block label) (in); default 4 | |
| block_length_in | No | Block face length (from the block label) (in); default 12 | |
| trench_width_in | No | Base trench width (in); default 24 | |
| exposed_height_in | No | Exposed wall height above grade (including cap) (in); default 24 | |
| length_or_diameter_ft | No | Wall length (straight) or outside diameter (circle) (ft); default 20 |