EstimatorPad

Rip Rap Calculator

Estimate riprap rock for a measured bank or flat bed. Calculate the real slope-face width from horizontal run and rise, then use the designed layer thickness and supplier bulk density.

Enter measurements below. Results update as you type, and optional prices can be added before sharing the estimate.

MEASURED MATERIAL TAKEOFF

Estimate rip rap quantities

Use measured dimensions and the exact product or supplier values. The starting measurements are a worked example.

ft
ft

For a measured slope-face width, enter that width here and set rise to zero.

ft

Zero gives a flat rectangular rock bed.

in

Thickness measured normal to the slope face; use the project design.

US ton/yd³

Use loose bulk density including voids, not solid-rock particle density.

USD/US ton
%

Local calculations. No signup required.

Measure horizontal run and vertical rise to find the slope faceHorizontal runRiseActual slope width
Illustration only. Rock volume uses the slope face and the entered normal layer thickness. Toe trenches and irregular areas are additional quantities.

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The calculation

Rip Rap Calculator method

Slope width = √(horizontal run² + rise²); rock volume = length × slope width × normal thickness; mass = volume × bulk density

  • Use consistent length units before multiplying; thickness is converted separately from inches or centimetres.
  • For a measured slope-face width, enter it as the horizontal run and set rise to zero. Do not apply the slope correction twice.
  • Waste is applied once to rock volume. Bulk density must include the spaces between rocks; particle density would overstate the order mass.
  • The tool estimates material quantity, not D50 rock sizing, rock class, hydraulic stability or erosion-control design. Toe trenches, bedding and filters are separate quantities.

Quick examples

30 ft length, 4 ft horizontal run, 3 ft rise5 ft slope-face width
12 in normal thickness150 cu ft before allowance
10% allowance, 1.4 US short tons/cu yd6.111 cu yd; about 8.556 US short tons

Examples are planning checks. Product-label coverage and whole pack sizes control the final purchase quantity.

Verified references

Check the exact product data before ordering

USACE HEC riprap and scour calculator

Authoritative reference distinguishing hydraulic rock sizing and scour analysis from a material quantity takeoff.

Open source

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Common questions

Understand the result before purchasing

01How many tons of rip rap do I need?+

Calculate the actual surface area along the bank, multiply by the designed layer thickness, add the allowance and multiply by the supplier’s bulk tons-per-yard value.

02Should I measure the bank horizontally or along the slope?+

The calculator derives the slope-face width from horizontal run and rise. If you already measured along the slope, enter that measurement as the run and set rise to zero.

03Is a ton the same as a metric tonne?+

No. The imperial result uses US short tons of 2,000 lb. Metric mode uses tonnes of 1,000 kg and converts the editable bulk density.

04Does this choose the rock size or required thickness?+

No. Use the project design for rock grading and normal layer thickness. Hydraulic and erosion-control sizing are separate engineering tasks.

05Does it include delivery, filters or toe trenches?+

No. The optional USD price covers the estimated rock mass only. Delivery, placement, filter materials, bedding and toe details are excluded.