Retaining Wall Calculator
How many blocks for a retaining wall? Enter the wall length and height and block size, and get blocks, cap blocks and gravel backfill — with the permit warning for walls over 4 ft.
Walls over 4 ft usually need engineering and a permit — check local rules.
Retaining wall — 60 sq ft of face
199 blocks — 9 courses · 20 cap blocks
Face area: 60 sq ft (5.6 sq m). Gravel backfill behind the wall (12 in deep, full height): 2.22 cu yd (1.70 cu m) — plus a perforated drain pipe at the base, which is what actually keeps a retaining wall standing. Walls over 4 ft tall usually need an engineer and a permit; check local rules before building.
Estimate. Block face sizes vary by product — confirm the actual dimensions and current prices with the supplier. Buried courses (one course below grade for every 8 in of height) are not counted here; add them to the height.
Formula used: Blocks = (length × height ÷ block face area) × (1 + waste%). Caps = wall length ÷ cap length. Backfill gravel = length × 1 ft deep × height ÷ 27 cu yd.
How this estimate works: The wall face is length times height, divided by the face area of one block, plus waste for cuts at the ends and around steps. Cap blocks run along the top, one per block length. The backfill is a 12-inch column of gravel behind the whole wall — it drains water away from the face, and without it hydrostatic pressure will push the wall over.
How the retaining wall calculator works
The wall face is length times height, divided by the face area of one block, plus waste for cuts at the ends and around steps. Cap blocks run along the top, one per block length. The backfill is a 12-inch column of gravel behind the whole wall — it drains water away from the face, and without it hydrostatic pressure will push the wall over. Walls over 4 ft tall usually need an engineer and a permit; check local rules before building. Buried courses are not counted here, so add them to the height.
Try next: Concrete Calculator · Concrete Bags Calculator · Mortar Calculator
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