Landscape Retaining Wall Calculator
Estimate retaining wall blocks, base gravel, and drainage for landscape walls. Enter wall length and height for block count and backfill materials.
Built for Landscaping1 documented formulaFocused single-task workflowPrivate in your browser
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A quick decision brief for this specific tool
Inputs that matter
Wall Length, Wall Height, Block Length, Block Height
Output to expect
Retaining Wall Calculator
How it works
1 documented formula across 1 calculation mode
- Confirm that every value uses the unit and time basis shown before comparing scenarios.
- Change one input at a time to see which assumption materially changes the result.
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Reference & details
How it works
Updated July 2026
How it works
Updated July 2026Block Count
Wall face area = length × height. Divide by one block face area. Add 5% for cuts and caps.
Blocks = ceil(Wall Face Area ÷ Block Face Area × 1.05)Gravel Base Trench
Buried course plus 6″ compacted gravel base in trench width of 24″ minimum.
Base (cu yd) = Length × Trench Width × Depth ÷ 27Drainage Aggregate
Free-draining aggregate behind wall to daylight or drain pipe. Critical for hydrostatic pressure relief.
Drainage = Wall Height × Length × 12″ thick ÷ 27 cu ydUpdated: July 2026
Example Scenarios
120 sq ft face with 12×4×8″ blocks ≈ 540 blocks + cap units. No geogrid typically under 3 ft in stable soil.
4 ft height may need geogrid every 2 courses per manufacturer. Engineer required over 4 ft in many jurisdictions.
Curved wall uses more cut blocks — 10% waste. Compact base trench on undisturbed soil.
FAQ
Most segmental block manufacturers allow DIY to 3–4 ft with proper base and drainage. Over 4 ft typically requires engineered design and permits.
Yes for walls over 18″ — perforated pipe at base behind wall draining to daylight. Without drainage, hydrostatic pressure collapses walls.
Excavate to firm subgrade. 6″ compacted gravel base, level front-to-back and side-to-side. First course partially buried.
Manufacturer specs require geogrid reinforcement at height thresholds (often every 2 ft above 3 ft). Grid extends into retained soil 60–80% of wall height.
Cap blocks finish the top course and glue with concrete adhesive. Order caps = wall length ÷ cap length, rounded up.
About Landscape Retaining Wall Calculator
Plan segmental retaining wall materials before starting a garden or terrace project. Enter wall length, height, and block dimensions to get block count, gravel base, drainage aggregate, and geogrid layers for walls over 4 ft.