How much riprap do I need?
Riprap is large, angular stone placed on slopes, culverts, and shorelines to slow water and stop erosion.
Enter the length, width, and depth of your area above. The calculator shows cubic yards, cubic feet, an estimated weight in tons, and the number of bags if you buy bagged riprap. Add a price per cubic yard and it also estimates the cost.
Cubic yard calculator for riprap
This cubic yard calculator for riprap works for any shape. Pick rectangle for most beds and slabs, circle for round areas, or trench for narrow runs. Open the price estimator under the calculator to add your supplier price, delivery fee, and tax. For a full cost breakdown, see the cubic yard price estimator.
Riprap weight and bags per cubic yard
A planning value for riprap is 3,000 pounds per cubic yard, which is 1.50 US tons. Moisture, particle size, and compaction move that number, so treat it as a starting point.
| Measure | Value |
|---|---|
| Pounds per cubic yard | 3,000 |
| US tons per cubic yard | 1.50 |
| Kilograms per cubic yard | 1,361 |
| Cubic yards per US ton | 0.67 |
| Cubic feet per US ton | 18.00 |
How far does a cubic yard of riprap go?
Coverage depends only on depth. The deeper the layer, the less area a cubic yard covers. The suggested depth for riprap is 12 to 36 inches, and 18 inches is a common choice.
| Depth (inches) | Square feet covered | Square yards covered |
|---|---|---|
| 1 | 324 | 36.0 |
| 2 | 162 | 18.0 |
| 3 | 108 | 12.0 |
| 4 | 81 | 9.0 |
| 6 | 54 | 6.0 |
| 8 | 40 | 4.5 |
| 12 | 27 | 3.0 |
| 18 | 18 | 2.0 |
| 36 | 9 | 1.0 |
Riprap needed for common areas at 18 inches deep
| Area | Square feet | Cubic yards | US tons |
|---|---|---|---|
| 5 by 5 ft | 25 | 1.39 | 2.08 |
| 8 by 10 ft | 80 | 4.44 | 6.67 |
| 10 by 10 ft | 100 | 5.56 | 8.33 |
| 10 by 20 ft | 200 | 11.11 | 16.67 |
| 12 by 12 ft | 144 | 8.00 | 12.00 |
| 15 by 20 ft | 300 | 16.67 | 25.00 |
| 20 by 20 ft | 400 | 22.22 | 33.33 |
| 20 by 30 ft | 600 | 33.33 | 50.00 |
| 30 by 40 ft | 1,200 | 66.67 | 100.00 |
| 50 by 50 ft | 2,500 | 138.89 | 208.33 |
Worked example: 30 by 6 feet at 18 inches
The area is 30 feet times 6 feet, or 180 square feet. A depth of 18 inches is 1.50 feet. Volume is 180 times 1.50, which is 270.00 cubic feet. Divide by 27 to get 10.00 cubic yards. At 3,000 pounds per cubic yard that weighs about 15.00 US tons. With 10 percent extra, order 11.00 cubic yards.
Tips for ordering riprap
- Layer thickness depends on stone size and slope, so use the thickness on your plan.
- A fabric underlayer keeps soil from washing out between the stones.
- For drainage or shoreline work, follow local rules and an engineer or agency guidance.
Riprap is usually priced by the ton, and big stones leave gaps, so confirm the weight per cubic yard with the quarry.
Frequently asked questions
How many cubic yards of riprap do I need?
Multiply length, width, and depth in feet, then divide by 27. A 30 by 6 foot area at 18 inches deep needs about 10.00 cubic yards.
How much does a cubic yard of riprap weigh?
About 3,000 pounds, or 1.50 US tons, as a planning value. Ask your supplier for the exact figure.
How deep should riprap be?
Most projects use 12 to 36 inches. 18 inches is a common choice.
How many square feet does a cubic yard of riprap cover?
18 square feet at 18 inches deep, and 324 square feet at 1 inch.