Rip Rap Calculator
Size a rip rap stone layer for a slope, shoreline, ditch, or channel. Enter the coverage length and width and the rip rap thickness, pick a stone type, and get the volume in cubic yards, the weight in tons, the number of truckloads, and the cost by the ton — with by-thickness and by-stone tables and a downloadable PDF.
| Thickness | Cubic yards | Tons | Loads |
|---|---|---|---|
| Enter coverage to see thicknesses | |||
| Stone | Density | Tons | Loads |
|---|---|---|---|
| Enter a volume to compare stone | |||
How to use the rip rap calculator
Enter the coverage length and width and the rip rap thickness, pick the stone type, add a waste allowance and a price per ton, and get the volume in cubic yards, the weight in tons, the number of truckloads, and the cost — plus reference tables for thickness and stone type.
Enter the coverage
Length, width and thickness, each with its own unit. For a slope, measure up the slope face, not the horizontal run.
Pick the stone
Choose limestone, granite, sandstone and more — it sets the placed density used to turn volume into tons.
Add waste & price
Set a 10–15% overage for settling and toe keying, a price per ton, and the delivery truck size.
Read tons & save a PDF
See tons, cubic yards, truckloads and cost, compare thicknesses and stone types, and download the report.
How a rip rap order is calculated
It’s a volume problem with one twist: rip rap is bought by weight, not volume. Work out the cubic yards of stone, add an overage, then convert to tons using the placed density of your stone — voids and all.
Worked example — a 20 × 12 ft slope, 18 in of limestone, 10% waste
Volume: 20 × 12 × 1.5 = 360 ft³
Cubic yards: 360 ÷ 27 = 13.33 yd³
With waste: 13.33 × 1.10 = 14.67 yd³
Tons: 14.67 × 1.35 = 19.8 tons
Trucks: roundup(19.8 ÷ 15) = 2 loads
About 19.8 tons of limestone — two tandem-dump loads — to armor 240 square feet at 18 inches.
Rip rap coverage & tonnage charts
The lookups that come up most — how far a ton goes at each thickness, placed densities by stone, tons by coverage area, and truck payloads for planning deliveries.
| Thickness | Sq ft per ton | Sq ft per yd³ | Tons per 100 sq ft |
|---|---|---|---|
| 4 in | 60 sq ft | 81 sq ft | 1.7 tons |
| 6 in | 40 sq ft | 54 sq ft | 2.5 tons |
| 9 in | 27 sq ft | 36 sq ft | 3.7 tons |
| 12 in | 20 sq ft | 27 sq ft | 5.0 tons |
| 18 in | 13 sq ft | 18 sq ft | 7.5 tons |
| 24 in | 10 sq ft | 13.5 sq ft | 10.0 tons |
Coverage per ton halves when thickness doubles — thickness is a straight multiplier on tonnage. Figures use a placed limestone density of about 1.35 tons per cubic yard before any waste allowance.
| Stone | Placed density | Tons per yd³ | Relative weight |
|---|---|---|---|
| Sandstone | 2,600 lb/yd³ | 1.30 t/yd³ | Lightest |
| Broken concrete | 2,600 lb/yd³ | 1.30 t/yd³ | Light, recycled |
| Limestone | 2,700 lb/yd³ | 1.35 t/yd³ | Common default |
| Granite | 2,800 lb/yd³ | 1.40 t/yd³ | Heavier, durable |
| Field stone | 2,900 lb/yd³ | 1.45 t/yd³ | Dense |
| Gabion rock | 3,000 lb/yd³ | 1.50 t/yd³ | Heaviest |
These are placed densities — they already include the voids between stones, so they run lighter than solid rock. The same volume in granite weighs roughly 10% more than in sandstone, which is why stone choice changes the tonnage you order.
| Area | Cubic yards | Tons | Truckloads (15 t) |
|---|---|---|---|
| 100 sq ft | 3.7 yd³ | 5.0 tons | 1 |
| 250 sq ft | 9.3 yd³ | 12.5 tons | 1 |
| 500 sq ft | 18.5 yd³ | 25.0 tons | 2 |
| 1,000 sq ft | 37.0 yd³ | 50.0 tons | 4 |
| 2,500 sq ft | 92.6 yd³ | 125.0 tons | 9 |
| 5,000 sq ft | 185.2 yd³ | 250.0 tons | 17 |
Scale these for your thickness: 18 inches is 1.5× the tons shown, 24 inches is 2×, 6 inches is half. Truckloads round up to whole deliveries and assume a 15-ton tandem dump.
| Truck | Typical payload | Cubic yards (limestone) |
|---|---|---|
| Single-axle dump | ~10 tons | ~7.4 yd³ |
| Tandem dump | ~15 tons | ~11.1 yd³ |
| Tri-axle dump | ~20 tons | ~14.8 yd³ |
| Quad / semi end-dump | ~25 tons | ~18.5 yd³ |
Payloads are typical and vary with local road limits and the truck. A partial load still ships as a full delivery and most quarries set a minimum, so size the job against whole loads where you can.
Rip rap is a layer of loose graded stone over a filter, sized by the coverage area and the thickness. You calculate the volume, but you buy the tonnage — and placed stone carries voids, so it weighs less than solid rock.
- Thickness drives the order — it’s a direct multiplier, so 18″ instead of 12″ is 50% more stone.
- Measure the slope face — use the distance up the slope, not the horizontal run, or you’ll under-order.
- The filter is separate — this sizes the stone only; budget the geotextile or filter aggregate on its own.
Everything the calculator works out
One set of measurements gives you the volume, the tonnage, the truckloads and the cost, plus a comparison across thicknesses and stone types — and a report you can take to the quarry.
The figures behind every rip rap order
Built for anyone armoring against water
A lakefront bank, a culvert outlet, a drainage ditch, a graded spillway — the volume-to-tons math is the same, and ordering the right tonnage the first time keeps a job from stalling on a half-empty second delivery.
Protecting a lakefront bank or a washing-out slope, and wanting the tonnage and the delivery count right before calling the quarry.
- Measure up the slope face
- Start with 12–18″ thickness
- Plan for a filter fabric under
Lining a swale or dry creek bed and pricing stone across a few sections, comparing stone types on look and cost.
- Compare stone types for weight
- Add each run as an area
- Order by the ton, not the yard
Bidding channel or outlet armor to a class and thickness spec, reconciling tonnage with truckloads and haul cost.
- Match thickness to the stone class
- Size the job to whole loads
- Save the PDF with the bid
7 tips for ordering rip rap without errors
The assumptions that quietly put a stone order short — or leave rip rap failing within a season — and the checks that catch them before the truck is loaded.
Rip rap FAQ
The sizing, weight and ordering questions people ask most when armoring a slope, bank or channel with stone.
Multiply length by width by thickness, all in feet, then divide by 27 for cubic yards. Multiply the cubic yards by the stone’s placed density in tons per cubic yard to get the tonnage you order against.
For a 20-by-12-foot slope at 18 inches: 20 × 12 × 1.5 = 360 ft³, or 13.33 yd³, which is roughly 18 tons of limestone before waste. Rip rap is sold by the ton, so tons is the number the quarry quotes.
The standard rule is 1.5 to 2 times the diameter of the largest stone, and never less than the largest stone itself. In practice that puts most slope and channel armor between 12 and 24 inches, with the deeper end for higher-energy water.
Thickness is a direct multiplier on volume and tonnage, so 12 to 18 inches raises the order by half. Confirm the required thickness and stone class with your engineer or the agency spec — under-thickness is the common cause of rip rap failure.
Placed rip rap runs about 1.25 to 1.5 tons per cubic yard, depending on rock type, gradation and voids. Limestone is near 1.35 tons, granite about 1.4, and dense field stone or gabion rock can reach 1.5.
That’s the placed density, which already includes the air gaps between stones, so it’s lighter than solid rock. Use it to turn volume into the tonnage you buy, but treat it as an estimate and confirm with your quarry — gradation and moisture both move it.
Rip rap is almost always sold and delivered by the ton. Quarries price large graded stone by weight because it loads and hauls by weight, and because the void fraction makes a cubic-yard price unreliable.
That’s why this calculator works out volume first, then converts to tons using the placed density of the stone you pick. Order against the tonnage, but keep the cubic-yard figure as a check on how much space the delivery will fill.
Stone size is driven by the water’s energy. Gentle swales and light erosion control use 4 to 8 inch stone; typical shoreline and slope protection uses 9 to 18 inch; fast channels, spillways and wave-exposed banks need 18 inch and larger.
Agencies publish graded classes (a state DOT Class I/II/III, or an FHWA designation) that fix the size distribution for a given flow. Pick the class from the spec or your engineer, then set thickness to 1.5–2× that stone’s size.
Divide total tonnage by the truck payload and round up. A single-axle dump carries roughly 10 tons, a tandem about 15, a tri-axle around 20, and a quad or semi end-dump up to 25 tons per load.
Rounding up matters because a partial load still ships as a full delivery, and most quarries set a minimum. Just over a truckload, it’s often cheaper to trim the design slightly or take a little extra on one load than to pay for a second nearly empty run.
Almost always. Rip rap armors the surface but water still moves through the voids, and without a barrier it washes the soil out from underneath until the stone slumps. A granular filter or a geotextile fabric between the subgrade and the stone stops that piping while still draining.
The filter isn’t optional on most engineered jobs, and this calculator sizes only the stone, not the filter. Budget for the fabric or filter aggregate separately, and follow the spec for its gradation or fabric class.
Add about 10 to 15 percent to the calculated volume. Rip rap settles into the subgrade, needs extra at the keyed-in toe below grade, and never places to a perfectly even thickness over rough ground, so the bare geometric volume always runs short.
Add toward the higher end for steep slopes, irregular banks, or a keyed toe trench running the full length. Running short mid-placement means a second delivery and often a second minimum charge, so a modest overage is cheaper than a return trip.
Estimation Only — Confirm Class, Thickness and Tonnage: This calculator works out rip rap volume from the dimensions you enter (volume = length × width × thickness ÷ 27) and converts it to tons using typical placed-stone densities. Those densities include the voids between stones and vary with rock type, gradation, moisture and how the stone is placed, so the tonnage is an estimate. Thickness is commonly 1.5–2× the largest stone; the correct stone class, layer thickness and filter requirement for a given flow must come from your engineer or the governing agency spec, and are a safety matter on erosion-control and channel work. The calculator sizes the stone only, not the filter fabric or granular filter layer beneath it. Truckloads assume typical payloads that vary with local road limits. Prices shown are whatever rate you enter and are not quotes. For estimation purposes only; confirm the stone class, thickness, tonnage and filter design with your engineer or supplier before ordering.