River Rock Calculator

River rock is sold by the ton or the cubic yard in bulk and by the bag in stores. The calculator works out the volume, then the weight from the weight of loose rock, so you can compare a bulk delivery with a pile of bags.

How to use this calculator

1. Choose the shape and enter its size. For a ring around a tree, enter the outer and inner diameter.
2. Enter the depth of rock you want. A bed of decorative rock is usually a few inches deep.
3. Add more areas if you have several beds or a path, and order the total.

Worked examples

How much river rock weighs

Loose rock weighs about 95.2 lb per cubic foot, from a Los Angeles County Public Works conversion table, or about 1.29 tons per cubic yard. One rock supplier figures 1.25 tons per cubic yard for most landscape rock, so a yard and a ton are close enough to order by either.

Bagged river pebbles come in bags of about 0.5 cubic feet, weighing about 40 lb. Bags make sense for a small bed; for anything bigger, bulk rock by the ton or yard costs far less.

How deep to lay it

A bed of landscape rock is usually laid 2 to 3 inches deep, and Colorado State University suggests about 3 inches for rock or gravel mulch. Larger rock needs more depth to cover the ground between the stones.

Rock does not stop weeds as well as you might hope: stones bigger than about 0.5 inch leave gaps that weed seeds settle into. Under a thin layer of rock, porous landscape fabric helps; New Mexico State finds it useful when the covering is less than 3 to 4 inches thick.

Before you order

• Rock is hard to remove once it is down, so be sure of the spot: extension services warn that taking rock out later is slow and costly.
• Edge the bed with steel, stone or plastic edging so the rock stays put.
• Bulk loads come by the ton or the yard, often with a minimum and a delivery fee; ask the yard which it uses before you compare prices.

Common questions