Rip Rap Calculator

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Calculates the appropriate rip rap size for erosion control based on flow velocity and other factors.

How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Flow Velocity (ft/s), Rock Shape Factor, Rock Density (lb/ft³), and Safety Factor in the units shown.

Step 2

Read Minimum Rock Diameter (ft) and Recommended Rock Diameter (in) in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

See the inputs and their calculated results.

Flow Velocity (ft/s): 2 ft/s; Rock Shape Factor: 0.85; Rock Density (lb/ft³): 165 lb/ft³; Safety Factor: 1.2

Minimum Rock Diameter (ft): 1.118719389 ft; Recommended Rock Diameter (in): 13.42463267 in

Flow Velocity (ft/s): 4 ft/s; Rock Shape Factor: 0.85; Rock Density (lb/ft³): 165 lb/ft³; Safety Factor: 1.2

Minimum Rock Diameter (ft): 4.474877556 ft; Recommended Rock Diameter (in): 53.69853067 in

Flow Velocity (ft/s): 6 ft/s; Rock Shape Factor: 0.85; Rock Density (lb/ft³): 165 lb/ft³; Safety Factor: 1.2

Minimum Rock Diameter (ft): 10.0684745 ft; Recommended Rock Diameter (in): 120.821694 in

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