How thick should rip rap be?

At least 1.5 to 2 times the median stone size (D50), and never less than 12 inches. Class II rip rap with a 9 inch median is usually placed 18 inches thick.

How much does rip rap weigh per cubic yard?

Placed rip rap weighs about 1.3 to 1.5 tons per cubic yard. The stone itself is heavier, but the large voids between rocks bring the in-place density down.

How much does rip rap cost?

Rip rap stone costs roughly $45 to $85 per ton delivered, depending on class and haul distance. Placement with an excavator often costs as much again, especially on steep or wet banks.

Do you need fabric under rip rap?

Yes. Without a filter layer, water moving through the stones pulls the soil out from underneath and the rip rap slumps. Use a heavy non-woven geotextile or a 6 inch bedding layer of smaller stone.

Drainage & Base

Rip Rap Calculator

Rip rap is laid as a blanket at least one and a half to two times as thick as the median rock size. Pick the rip rap class and the slope dimensions, and this calculator sets the blanket thickness, then returns the volume, tonnage, truck loads, and the filter fabric that must go underneath.

What you'll need

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Prices as of Sep 25, 2026, 6:18 PM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.

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Frequently asked questions

How thick should rip rap be?: At least 1.5 to 2 times the median stone size (D50), and never less than 12 inches. Class II rip rap with a 9 inch median is usually placed 18 inches thick.
How much does rip rap weigh per cubic yard?: Placed rip rap weighs about 1.3 to 1.5 tons per cubic yard. The stone itself is heavier, but the large voids between rocks bring the in-place density down.
How much does rip rap cost?: Rip rap stone costs roughly $45 to $85 per ton delivered, depending on class and haul distance. Placement with an excavator often costs as much again, especially on steep or wet banks.
Do you need fabric under rip rap?: Yes. Without a filter layer, water moving through the stones pulls the soil out from underneath and the rip rap slumps. Use a heavy non-woven geotextile or a 6 inch bedding layer of smaller stone.