In short
- A riprap tonnage calculator turns wall length, rock width and rock height into cubic yards, then tons.
- Solid riprap stone typically weighs 150 to 175 pounds per cubic foot, and 165 is a common assumption (US Army Corps of Engineers EM 1110-2-1601). Placed rock weighs less, because of the gaps between rocks.
- Florida's highway specification pays for riprap by the ton on scale weight, so quotes and delivery tickets come in tons.
- Florida's general permit for rock at a seawall toe limits the slope to 2:1 and the width to 10 feet from the wall. The calculator flags numbers outside that.
On this page
This riprap tonnage calculator is for rock placed at the base (the toe) of a Cape Coral seawall. You enter the wall length, the width and height of the rock, and the placed weight of the stone. It returns tons to order, truckloads and a cost if you add a price per ton. It is a planning estimate, not a quote or a design.
En español: Calculadora de toneladas de riprap para la base de un muro (Cape Coral)
| Your numbers | Result |
|---|
How the math works
- Cross-section area.
A wedge is width x height / 2. A full block is width x height. Both are in square feet.
- Volume.
Area x wall length gives cubic feet. Divide by 27 for cubic yards.
- Placed weight.
Use the supplier's tons per cubic yard. Or take the stone's pounds per cubic foot x 27 / 2,000 for solid tons per cubic yard, then keep only the share that is not open space.
- Tons to order.
Cubic yards x tons per cubic yard, plus your allowance. Divide by the hauler's load size and round up for truckloads.
Table: how much rock a 100-foot wall takes before weight
Plain geometry for wedges at a 2:1 slope (width twice the height), the steepest the state toe-rock permit allows. Multiply cubic yards by your supplier's tons per cubic yard.
| Wedge, width x height | Area (sq ft) | Cu yd per 100 ft |
|---|---|---|
| 4 ft x 2 ft | 4 | 14.8 |
| 6 ft x 3 ft | 9 | 33.3 |
| 8 ft x 4 ft | 16 | 59.3 |
| 10 ft x 5 ft | 25 | 92.6 |
Rock at a seawall toe needs permission first. Florida's general permit for riprap (Rule 62-330.431) limits the slope to 2:1, the distance to 10 feet from the wall, and the stone to one to three feet across, and the city or federal agencies can add steps. Read our riprap and sloped bank guide and seawall permits guide before you order any stone.
Where the stone weight comes from
| Figure | What it is | Value |
|---|---|---|
| Solid stone | Typical unit weight of riprap stone | 150-175 lb/cu ft |
| Solid stone | Common assumption | 165 lb/cu ft |
| Placed rock | Solid weight less the open space | Ask the quarry |
The Corps of Engineers figures describe the stone itself. Rock dumped in place has gaps between pieces, so a cubic yard of placed riprap weighs less than a cubic yard of solid stone. That is why the supplier's tons-per-cubic-yard figure is the one to use. Florida's highway specification (Section 530) also sets a minimum bulk specific gravity for riprap rubble. It was 2.30 in the 2009 version we checked and may have changed since, so ask which stone your quote covers.
What the estimate leaves out
- Stone grading and size. Size and the mix of sizes change the voids and the price per ton.
- Filter fabric and bedding stone. Rock often sits on fabric or a bedding layer. Those are separate quantities, and Florida's highway specification prices bedding stone by the ton as its own item.
- Uneven canal bed. A sloping or soft bed changes the real volume. Ask for a measured profile.
- Placement and labor. Barge or crane time, access and disposal are not in the tons.
- Permits and engineering. Fees and plans are separate from the rock.
Questions to ask before you accept a riprap quote
- What stone, and what size? Ask for type, size range and the quarry's weight per cubic yard in writing.
- Is the quote by the ton or by the job? A per-ton quote moves with the scale tickets; a job price fixes the risk on the contractor.
- Which permit covers this? Ask who files it, and get the number before work starts.
- Is fabric or bedding stone included? And who removes spoil and leftover rock?
- How is the rock measured and checked? Ask to see delivery tickets.
The seawall bid comparison calculator helps line up quotes, and how to choose a seawall contractor covers the rest. Planning for a whole wall? Try the seawall cost calculator. For why the toe matters, see seawall maintenance.
Next step: get real quotes
This result is a planning estimate, not a quote. Local providers can give a written quote through the request form on this page. We are a referral service, not a contractor; we connect visitors with independent local providers. Use the form below to ask for itemized quotes that show tons, price per ton and permits.
Sources
- Riprap characteristics, course slides summarizing US Army Corps of Engineers EM 1110-2-1601, Colorado State University: unit weight of riprap stone typically 150 to 175 pounds per cubic foot, 165 a common assumption. The manual itself is EM 1110-2-1601.
- Design Standards No. 13, Chapter 7: Riprap Slope Protection, US Bureau of Reclamation: rounded rocks fit together more tightly and reduce void space.
- FDOT Standard Specifications Section 530, Riprap (July 2009 workbook): rubble measured and paid by the ton on scale weight, minimum bulk specific gravity 2.30 in that version.
- Fla. Admin. Code R. 62-330.431, General Permit for Installation of Riprap: toe-rock limits, as summarized on our riprap guide.
Frequently asked questions
How many tons of riprap do I need for a seawall?
Multiply the length of wall by the cross-section area of the rock to get cubic feet, divide by 27 for cubic yards, then multiply by the placed weight in tons per cubic yard. The calculator does this for you. The placed weight depends on the stone and on the gaps between the rocks, so use your supplier's figure when you have it.
How much does a cubic yard of riprap weigh?
It depends on the stone and on how much open space sits between the rocks. The Army Corps of Engineers manual EM 1110-2-1601 gives a typical unit weight for solid riprap stone of 150 to 175 pounds per cubic foot, with 165 a common assumption. Placed rock weighs less than that, because the gaps are empty. Ask the quarry for the tons per cubic yard it expects.
Can I add rock at the base of my seawall without a permit?
Do not assume so. Florida has a general permit for riprap at the toe of an existing vertical seawall, with limits on slope (2:1), distance from the wall (10 feet), stone size and material, and the city or federal agencies can add steps. Read our riprap guide and confirm with the City of Cape Coral and the Florida Department of Environmental Protection before ordering stone.
How many truckloads will the rock take?
Divide the tons you order by the tons your hauler carries per load, and round up. Truck capacity varies by truck and by road weight limits, so enter your hauler's number. The calculator leaves it blank rather than guess.