Rip Rap Calculator
Calculate tons of rip rap armor stone for a bank or shoreline using its 1.5 tons per cubic yard density, plus total material cost.
How this calculator works
Rip rap is sold by weight but measured by volume, so this calculator converts your bank length, protected width, and placement depth into cubic yards, then multiplies by rip rap’s typical density of 1.5 tons per cubic yard to get the tons you need to order.
Formula: Cubic yards = (Bank length ft × Protected width ft × Depth ft) ÷ 27. Tons = Cubic yards × 1.5.
Worked example
A 30 ft bank section, protected 6 ft up-slope, placed at a 12-inch depth:
- Depth in feet: 12 ÷ 12 = 1.0 ft
- Cubic yards: (30 × 6 × 1.0) ÷ 27 ≈ 6.6667 yd³
- Tons: 6.6667 × 1.5 ≈ 10.00 tons
- At $60/ton, that’s $600.00 before waste.
Coverage reference
| Bank length × protected width | Tons needed (at 12 in) |
|---|---|
| 15 ft × 3 ft | 2.50 tons |
| 30 ft × 6 ft | 10.00 tons |
| 60 ft × 12 ft | 40.00 tons |
How to measure your bank
Walk the bank or shoreline you’re protecting and measure its total length in feet, then measure up-slope from the normal waterline to the highest point expected flooding or wave splash will reach — that’s your protected width. Use the full placement depth specified for your stone size, not a compacted depth, since rip rap isn’t compacted like a base aggregate.
Frequently asked questions
What should I enter for Length and Width when calculating rip rap for a bank?
Length is the total run of bank or shoreline you're protecting, in feet. Width is the band of protected slope measured up from the waterline — how far up the bank the stone needs to extend to handle expected wave action or flood stage, also in feet.
Why is rip rap the heaviest common gravel-family material at 1.5 tons per cubic yard?
Rip rap is large, dense, angular armor stone specifically selected for mass — its whole purpose is resisting the force of moving water, so quarries grade it toward larger, heavier pieces rather than the more uniform, moderate sizing used in general aggregate.
What size stone counts as rip rap?
Rip rap generally ranges from about 6 inches up to 2 feet or more in individual stone size, graded to the expected water velocity and wave energy at the site — larger, faster water calls for larger stone so individual pieces aren't washed away.
Do I need a filter fabric or bedding layer under rip rap?
Yes, in almost every erosion-control application. A geotextile filter fabric (or a granular bedding layer) placed under the rip rap keeps the underlying soil from washing out through the gaps between the large stones, which would undermine the whole installation over time.
What depth of rip rap should I order for bank protection?
12 inches is a common minimum placement thickness for residential bank stabilization, though the right depth depends on stone size and expected water force — as a rule of thumb, the placed layer should be at least 1.5 times the diameter of the largest stones used.
Should I add waste when ordering rip rap?
Yes, the 10% waste toggle is a reasonable buffer for an irregular bank profile and the fact that large stone doesn't nest as tightly or predictably as smaller aggregate during placement.
Estimates only. Verify quantities with your supplier before purchasing.