Riprap Quantity Calculator
Estimate riprap or rock armor quantity from coverage area and thickness. Uses a typical stone unit weight so you can order by the ton or by the yard.
Enter your values, then press Calculate.
How to calculate
Enter the length and width of the armor area and the specified thickness (often 12–24 in). Use 1.4–1.7 tons/yd³ for most dumped riprap unless the spec gives a density. Add waste for over-placement and irregular subgrade.
Formula
Volume (ft³) = length × width × thickness. Cubic yards = ft³ ÷ 27. Tons = cubic yards × tons per cubic yard. Waste multiplies both.
Common use cases
- Channel lining takeoffs
- Outlet protection
- Slope armor
- Checking a quarry quote
Worked example
Example: 50 × 10 ft at 18 in, 1.5 t/yd³
1. Neat volume
50 × 10 × 1.5 = 750 ft³
2. Cubic yards
750 ÷ 27 = 27.7778 yd³
3. Tons
27.7778 × 1.5 t/yd³ = 41.6667 tons
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FAQ
Is 1.5 tons per cubic yard accurate?
It is a common field default for dumped riprap. Use the spec, quarry ticket, or lab density when you have it. Heavier stone or grouted riprap will weigh more.
Does this include filter fabric or bedding?
No. The result is stone volume and tons only. Filter fabric, bedding gravel, and grout are separate quantities.
Disclaimer
These calculators are estimating tools for planning and field checks. They are not a substitute for approved plans, specifications, licensed professional engineering, or governing standards. Confirm densities, waste factors, and yields with your supplier and project documents.