Construction calculators

Rip Rap Calculator

Updated Nov 10, 2026 By Infinity Calculator Formulas Sources
Rate
3,300
lb/yd³
1.650
t/yd³ (US short tons)
0.606
yd³/t
ft
ft

Select a rip rap class for a quick estimate. Each class covers the area per ton that Front Range Material publishes for its median stone size (D50).

Class L (D50 9")
About 23 ft² per ton
Class M (D50 12")
About 17 ft² per ton
Class H (D50 18")
About 11 ft² per ton
Class VH (D50 24")
About 8 ft² per ton
Rip Rap Estimation Results
Area 1,000.00 ft²
Volume 37.04 yd³
Weight 61.11 tons (122,222 lb)
Estimated Cost $2,750.00
Depth 12.0 in
Material Rip Rap (6–12")
Depth Sensitivity Analysis

See how varying depth affects your material requirements for the same area.

Depth (in) Volume (yd³) Weight (tons) Estimated Cost

Introduction

Rip rap is a layer of large, loose stones used to protect soil from erosion. It is commonly placed along shorelines, stream banks, bridge foundations, and slopes where water flow could wash away the ground. Our Rip Rap Calculator helps you figure out how much rip rap stone you need for your project. Just enter your measurements, and the tool will estimate the volume and weight of material required. This saves you time and helps you order the right amount of stone so you don't waste money on too much or too little material. This calculator makes planning simple and quick for projects from a small drainage ditch to a large embankment.

How to Use Our Rip Rap Calculator

Enter the details about your rip rap project area and stone type below. The calculator will tell you the volume, weight in tons, and estimated cost of material you need.

Calculation Method: Choose between the "Volume & Density Method" for precise results using exact dimensions, or the "Coverage Rate Method" for a quick estimate based on published coverage rates per ton.

Material Type: Pick the type of rip rap stone you plan to use, such as Gabion Stone, Bull Rock, or Large Boulders. The calculator weighs every rip rap size at the same density. You can also enter a custom density if your stone is not listed.

Unit System: Select Imperial (feet and inches) or Metric (meters and centimeters) depending on how your measurements are taken.

Area Shape: Choose the shape that best matches your project area: Rectangle, Circle, Triangle, Trapezoid, or enter the total area directly if you already know it.

Dimensions: Enter the measurements for your chosen shape. For a rectangle, type in the width and length. For a circle, enter the diameter. For a triangle, enter the base and height. For a trapezoid, enter the bottom width, top width, and height.

Depth / Thickness: Enter how deep or thick the rip rap layer needs to be. You can set the unit to inches, feet, centimeters, or meters using the dropdown next to this field.

Cost per Ton (optional): Type in the price you expect to pay per ton of rip rap. This lets the calculator show you a total estimated material cost. Leave it blank to skip the cost.

Stone Size Category (Coverage Rate Method only): If you use the quick method, pick a rip rap class: L, M, H or VH. Each class has a median stone size (D50) and a coverage rate in square feet per ton.2

Project Area (Coverage Rate Method only): Enter the total area in square feet that you need to cover with rip rap when using the quick estimate method.

What Is Rip Rap?

Rip rap is loose stone or rock placed along shorelines, slopes, channels, and other areas to protect against erosion caused by water flow. You will sometimes see it spelled as "riprap" or "rip-rap." It is one of the most common and effective erosion control materials used in construction. The stones are typically angular and rough. Angular stones interlock better than rounded stones of the same weight, which makes them more stable when water pushes against them.1

Common Types and Sizes of Rip Rap

Rip rap comes in many sizes, and the right choice depends on how fast the water moves and how much protection you need. Here are the sizes this calculator offers:

  • Gabion / Surge Stone (2–4" or 3–8"): Smaller stones often used inside wire baskets (gabions) or for light-duty drainage ditches and culvert outlets.
  • Bull Rock (4–12"): A versatile size popular for ditch lining, pond edges, and general slope protection.
  • Standard Rip Rap (6–12"): The most widely used size for stream banks, retention ponds, and stormwater channels.
  • Large Rip Rap (6–18"): Used where water flow is stronger, such as river banks and dam spillways.
  • Boulders (12–24"): The heaviest option, used for high-velocity water, coastal protection, and large-scale civil engineering projects.

How to Calculate How Much Rip Rap You Need

To figure out how much rip rap a project requires, you need three things: the area you want to cover, the depth (or thickness) of the stone layer, and the density of the material. The basic steps are:

  1. Find the area in square feet. This could be a rectangle, circle, triangle, trapezoid, or an irregular shape you measure directly.
  2. Determine the depth. Federal highway guidance says the stone layer should be at least as thick as the largest stone and at least 1.5 times the median stone size, whichever is thicker, and not less than 1 foot.1 For example, 6–12" rip rap needs a layer of at least 12 inches.
  3. Calculate the volume. Multiply area by depth to get cubic feet, then divide by 27 to convert to cubic yards.
  4. Convert to weight. Multiply the volume in cubic yards by the material's density in pounds per cubic yard, then divide by 2,000 to get US short tons.

Most rip rap is sold by the ton, so this last step is the most important for ordering and budgeting. This same volume-to-weight approach is used when estimating other bulk construction materials like gravel, sand, and concrete.

Rip Rap Density

Front Range Material converts rip rap at 1.65 tons per cubic yard.2 That is about 3,300 pounds per cubic yard.

Coverage Rate Method

If you want a quick estimate without doing a full volume calculation, you can use coverage rates. These tell you roughly how many square feet one ton of stone will cover. Front Range Material gives about 23, 17, 11 and 8 square feet per ton for class L, M, H and VH rip rap with a median stone size (D50) of 9, 12, 18 and 24 inches.2 Smaller stones cover more area per ton because they are placed thinner, while larger stones cover less.

Cost of Rip Rap

Rip rap prices vary by region, stone type, and delivery distance. Enter the price per ton from your supplier's quote to see the material cost. Delivery and installation can add significantly to the total price, so always get a quote that includes hauling when you budget your project.

Tips for Your Rip Rap Project

  • Use a geotextile fabric underneath the rip rap. This filter fabric prevents soil from washing out through the gaps in the stone.1
  • Match the stone size to the water speed. Faster water needs bigger, heavier rock to stay in place.
  • Check local regulations. Many areas have specific rules about rip rap size, placement, and permits near waterways.

Formulas used

Volume (Volume & Density Method)
V_{yd^3} = \frac{\text{Area}_{ft^2} \times \text{Depth}_{ft}}{27}
Weight from Volume
W_{tons} = \frac{V_{yd^3} \times \rho_{lb/yd^3}}{2000}
Estimated Cost
\text{Cost} = W_{tons} \times \text{Cost per Ton}
Coverage Rate Method (Quick)
W_{tons} = \frac{\text{Area}_{ft^2}}{\text{Coverage Rate}_{ft^2/ton}}
Density Conversions
\rho_{t/yd^3} = \frac{\rho_{lb/yd^3}}{2000}, \quad \text{yd}^3/\text{t} = \frac{2000}{\rho_{lb/yd^3}}
Area — Rectangle / Circle / Triangle / Trapezoid
A = L \times W, \quad A = \pi \left(\frac{d}{2}\right)^2, \quad A = \frac{1}{2}bh, \quad A = \frac{1}{2}(b_1 + b_2)h

Frequently asked questions

How many tons of rip rap do I need per square foot?

It depends on the stone size and depth. 1 ton of class L rip rap covers 23 square feet with a median stone size (D50) of 9 inches, and 1 ton of class VH rip rap covers 8 square feet with a D50 of 24 inches.2 For the volume method, multiply your area by the layer depth to get the volume, then convert it to tons using the density.

What depth of rip rap should I use?

Federal highway guidance says the layer should be at least as thick as the largest stone and at least 1.5 times the median stone size, whichever is thicker, and never less than 1 foot.1 It also calls for a layer 50% thicker when the rip rap is placed underwater.1 So for 6–12" rip rap, plan on a layer of at least 12 inches, and for 12–24" boulders at least 24 inches.

How much does a cubic yard of rip rap weigh?

Rip rap weighs about 1.65 tons per cubic yard.2 That is about 3,300 pounds per cubic yard, and the calculator uses it for every rip rap size it offers.

How do I convert rip rap volume from cubic yards to tons?

Multiply the cubic yards by the density in pounds per cubic yard, then divide by 2,000. For example, 10 cubic yards of standard rip rap (3,300 lb/yd³) equals 10 × 3,300 ÷ 2,000 = 16.5 tons.

How much area does 1 ton of rip rap cover?

It depends on the stone size and how thick you lay it. Front Range Material gives about 23, 17, 11 and 8 square feet per ton for rip rap with a median stone size (D50) of 9, 12, 18 and 24 inches.2 The quick method uses these four rates.

Why is rip rap sold by the ton instead of by the cubic yard?

Stone suppliers weigh trucks on scales when they load material, so selling by weight is more accurate and consistent. Volume can vary because of how the stones settle and stack, but weight stays the same. That is why most rip rap is priced and sold per ton.

Sources

  1. Lagasse PF, Clopper PE, Pagán-Ortiz JE, Zevenbergen LW, Arneson LA, Schall JD, Girard LG. Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance, Third Edition, Volume 2 (HEC-23, FHWA-NHI-09-112). Federal Highway Administration. 2009;Design Guideline 4, §4.2.3–4.2.6. Accessed September 26, 2026.
  2. Material Coverage & Conversion Chart. Front Range Material. Quick Conversion Factors (Rip Rap); Rip Rap Coverage. Accessed October 8, 2026.

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