Riprap Stone Calculator
What is Riprap Stone?
Riprap is a layer of large stones placed along riverbanks, slopes, or shorelines to prevent erosion caused by flowing water. It acts as a protective barrier that absorbs energy and stabilizes soil.
How to Calculate Riprap Stone?
To calculate riprap requirements:
- Measure length, width, and depth
- Calculate volume:
- Volume = Length × Width × Depth
- Multiply by density to get weight:
- Weight = Volume × Density
- Use velocity-based formula to find stone size
Typical Riprap Sizes
| Type | Size Range |
|---|---|
| Small | 4–5 inches |
| Medium | 6–9 inches |
| Large | 9+ inches |
These sizes vary depending on erosion intensity and water velocity
How Much Riprap Do I Need?
- Multiply area × thickness to get volume
- Recommended thickness = 2× stone size (D50)
Why This Calculator Matters
✔ Prevents under-sizing (erosion risk)
✔ Avoids over-spending on oversized stones
✔ Helps contractors estimate cost accurately
✔ Works for drainage, slopes, rivers, and landscaping
FAQs
What is D50 in riprap?
D50 is the median stone size where 50% of stones are smaller and 50% are larger.
What density should I use?
Typical range: 1600–2800 kg/m³ depending on rock type
Can I use this for landscaping?
Yes, but for decorative use you can ignore velocity and focus on volume only
