River Rock Calculator

Multiply the area you're covering by the depth, then convert to the unit river rock is sold in. In US units: area in square feet x (depth in inches / 12), then divide by 27 for cubic yards. In Metric: area in square meters x (depth in centimeters / 100) for cubic meters directly. Enter your unit system, dimensions, and depth above, and add a waste percentage if you want to account for spillage and an uneven base.

River rock bulk density varies by product, moisture, grading and supplier. This calculator therefore shows volume by default. Enter the bulk density provided by your supplier if you also need an estimated weight - suppliers typically determine this using a standard method such as ASTM C29 (Bulk Density and Voids in Aggregate).

Multiply the volume in cubic yards by the material's bulk density in pounds per cubic yard, then divide by 2,000 (the pounds in a US short ton). Because river rock density isn't fixed, use the figure your supplier provides - enter it in the optional Supplier density field above and the calculator does this conversion for you, in both US and Metric units.

Choose a bag size in the optional "Bag size" field - 0.5 or 1 cubic foot (US), 10, 20, or 25 liters (Metric), or "Custom" for a size not listed (entered in cubic feet if you chose US Customary, or liters if you chose Metric). The calculator divides your total order volume by the bag size and rounds up to a whole bag. Leave the field blank, or choose "Do not calculate bags," if you only want the bulk volume.

There's no single correct depth - it depends on the rock size, the look you want, and whether the rock sits over landscape fabric or bare soil. Larger rock generally needs more depth to look intentional and stay in place; smaller rock can work at a shallower depth. Decide your depth first, then use the calculator (or the coverage table below) to find the volume it requires - this calculator does not assume a depth for you.

Split the bed into simple shapes - rectangles, triangles, or circles - measure each one, calculate its area, and add the areas together. Use the Square Footage Calculator for shapes beyond a simple rectangle, then enter the total in this calculator's Known area mode. See the worked example below.

It depends on your total volume, what your local supplier sells, and your site access. Bags are easier to transport and store for small volumes or tight access, but cost more per cubic yard. Bulk delivery is cheaper per unit for larger volumes but usually has a minimum order and a delivery fee, and needs truck access to the drop location. Compare your calculated volume against your supplier's bag size and bulk pricing before deciding - see the ordering checklist below.

No. River rock is naturally rounded and smooth; crushed stone is often produced by crushing quarried rock or rounded pit/gravel-source material to change its shape. FHWA's Field Materials Manual associates that fractured, angular shape with aggregate interlock, and ASTM D5821 is the standard test method for determining the percentage of fractured particles in a sample - the basis for specifications that require a minimum fractured-face percentage. Rounded river rock stays relatively loose by comparison and should not be treated as equivalent to a properly specified, angular structural base. That's why crushed stone is used for compacted structural bases and river rock is used decoratively instead - see the Gravel Calculator for a structural base estimate.

River rock is commonly used as the visible, decorative layer over a French drain or to line a dry creek bed that directs surface water across a yard. It is not a substitute for an engineered subsurface drainage system - a French drain needs a perforated pipe, proper slope, and typically a fabric-wrapped angular aggregate fill, not just a rounded rock surface layer. This calculator estimates volume for the visible, decorative rock only, not a full drainage design.