Riprap Quantity Calculator

Plan durable rock protection with clear quantity outputs. Adjust for slope geometry, waste, and density. Download clean reports for bids, orders, and site checks.

Project Inputs
Choose geometry, then enter dimensions and material assumptions.
Geometry Dimensions
Slope length is computed from height and the H:1V ratio.
Typical bulk range: 1500–2000 kg/m³
Typical bulk range: 95–125 lb/ft³
Use >1.00 for loose placement and shape loss.
Covers spillage, sorting, and overbuild.
Adds extra area for overlaps and trimming.
The calculator reports volume and mass. Always verify thickness requirements, gradation, and placement method per project specifications.
Example Data Table
Scenario Geometry Key Inputs Typical Output
Riverbank protection Bank slope 50 m length, 3 m height, 2H:1V, 0.30 m thick Area ≈ 335 m², volume ≈ 106 m³ (before waste)
Apron at outfall Plan area 20 m × 5 m, 0.25 m thick, 5% waste Volume ≈ 26 m³, mass depends on density
Drainage channel lining Channel lining 100 m length, 4 m bottom, 1.5 m depth, 2H:1V Area ≈ 1030 m², volume ≈ 309 m³ (1 layer)
Example outputs are approximate and depend on placement factor and waste.
Formula Used
  • Plan area: A = L × W
  • Bank slope length: S = H × √(1 + (Hratio)²)
  • Bank area: A = ProtectedLength × S
  • Channel side length: S = √(D² + (Hratio × D)²)
  • Channel wetted perimeter: P = BottomWidth + 2 × S
  • Channel area: A = P × ChannelLength
  • Base volume: V = A × Thickness × Layers
  • Placed volume: Vp = V × PlacementFactor
  • Ordered volume: Vo = Vp × (1 + Waste%)
  • Mass: M = Vo × Density
  • Truckloads: N = M / TruckCapacity
Bulk density is used for ordering and trucking. Field compacted density can differ.
How to Use This Calculator
  1. Select the unit system used on your drawings.
  2. Pick the geometry that matches your protection area.
  3. Enter dimensions carefully, including side slopes when needed.
  4. Set thickness and layers based on project requirements.
  5. Confirm bulk density from the quarry or prior tickets.
  6. Use a placement factor to reflect loose placement or shaping loss.
  7. Add a realistic waste percentage for handling and overbuild.
  8. Click Calculate to view results above the form.
  9. Download CSV or PDF to attach to estimates and orders.
For critical works, validate against design guidance and site trials, and coordinate with supplier gradation and delivery constraints.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.