River Rock Calculator
Tonnage assumes about 1.35 tons per cubic yard. Wet stone weighs more, so a load delivered after heavy rain reads a little heavier on the scale.
River rock weighs about 1.35 tons per cubic yard, so a 10 by 10 foot bed at 2 inches deep needs roughly 0.62 cubic yards, or about 0.83 tons of stone. Set your area shape, dimensions, and depth below for exact cubic yards, tonnage, and cost — and remember a full yard is a heavy load, so check your delivery vehicle can carry it.
River rock coverage by area and depth
| Bed size | Cubic yards | Tons (at 1.35 t/yd) |
|---|---|---|
| 10 ft x 10 ft Area | 0.62 Yards | 0.83 Tons |
| 20 ft x 20 ft Area | 2.47 Yards | 3.33 Tons |
| 10 ft Circular Diameter | 0.48 Yards | 0.65 Tons |
| 20 ft Circular Diameter | 1.94 Yards | 2.62 Tons |
How to estimate river rock
River rock is ordered by volume and delivered by weight, so the estimate has two steps. First you work out how much space the stone fills; then you convert that to tons so you can compare quotes and check what your vehicle can haul. Because river rock is rounded and won't compact, there's no compaction allowance to add — what you order is roughly what you spread.
From area to cubic yards
Multiply the area you're covering by the depth of stone to get the volume. The calculator does this in cubic inches, then divides by 46,656 (the number of cubic inches in a cubic yard) to give you cubic yards, the unit most suppliers price in.
From there it applies a working density of about 1.35 tons per cubic yard to estimate weight. A single cubic yard runs close to 2,700 pounds, so it adds up fast — a mid-size pickup handles roughly half a yard safely. Confirm your supplier's tested density and your vehicle's load rating before a big order.
Choosing a river rock size
River rock is sold by size grade, and the grade you pick changes both how the surface looks and how it performs. Suppliers usually stock a handful of ranges, from pea-sized stone up to large cobble. The calculator works the same whichever grade you order — volume and weight per cubic yard don't shift much by size — but the right grade for the job is worth getting right before you buy.
Small: pea gravel to 3/4 inch
The smallest grades, from about 3/8 inch pea gravel up to 3/4 inch, sit flat and feel comfortable underfoot, so they suit walkways, play areas, potted-plant top-dressing, and fine decorative beds. Because the stones are small they also pack into tight spaces well, which is why 3/8 inch pea gravel doubles as a common drainage fill.
Medium: 1 to 3 inch
The 1 to 3 inch range — including the popular 1, 1 1/2, and 2 inch stones — is the workhorse for residential landscaping. It's the most common grade for decorative ground cover and garden beds because it reads as "river rock" at a glance without being so large it's awkward to rake or walk near. This range also handles most drainage work and edging around water features.
Large: 3 to 6 inch and cobble
Stone in the 3 to 6 inch range and larger cobble is used where you need mass rather than a fine finish: dry creek beds, swales, and erosion control on slopes, where big rounded stone stays put under moving water. It's too coarse for a walking surface, so it's a landscape feature, not a path material.
River rock by project
Landscaping beds and ground cover
For decorative beds, the 1 to 3 inch grade at 2 to 3 inches deep over landscape fabric is the standard choice. That depth covers the ground fully and suppresses weeds without stone shifting underfoot. Use the coverage figures above to order by the cubic yard — a 10 by 10 foot bed at 2 inches deep needs about 0.62 cubic yards — and round up rather than down, since a bed that's short of stone shows fabric through the gaps.
Drainage and erosion control
Drainage and erosion jobs split by scale. French drains and small drainage fills use smaller, well-sorted stone that lets water move through the voids; larger 3 to 6 inch stone armors dry creek beds and slopes against washout. Because river rock is rounded and won't compact, it drains freely by design — but that same rounding means it rolls on steep grades, so larger stone or a retaining edge matters more the steeper the slope.
Common mistakes when estimating river rock
The estimate itself is simple; the errors are usually in the setup. A few worth avoiding:
- Ordering by area and forgetting depth. Square footage alone doesn't tell you the volume — a bed covers the same area at 1 inch or 3 inches deep but needs three times the stone at the deeper setting.
- Underestimating the weight. River rock runs close to 2,700 pounds per cubic yard, so a "small" 2-yard order is well over 5,000 pounds. Match the load to your vehicle or arrange delivery.
- Picking the wrong grade. Fine stone on a slope rolls away; large cobble on a walkway is uncomfortable. Match the size to the job, not just the look.
- Skipping landscape fabric. Without a barrier, stone sinks into the soil and weeds push through, so you top up material and weed the bed for years.
For irregular beds, split the shape into rectangles and circles you can measure, run each through the calculator, and add the results. On sloped ground, measure the depth perpendicular to the slope rather than straight down so you don't under-order.
Frequently asked questions
How do you calculate how much river rock you need?
Multiply the area you're covering by the depth of stone, then convert to cubic yards. For a rectangular bed, that's length times width times depth; for a round area, use the diameter. A 10 by 10 foot bed at 2 inches deep works out to about 0.62 cubic yards, or roughly 0.83 tons. Enter your dimensions above and the calculator handles the conversion and the weight.
How much does a cubic yard of river rock weigh?
About 1.35 tons, or roughly 2,700 to 2,850 pounds. River rock is dense compared to mulch or soil, so a single cubic yard is a heavy load. The exact figure shifts with the parent rock and how wet the material is, so confirm the tested weight with your supplier on large orders.
How thick should I lay decorative river rock?
Lay decorative river rock 2 to 3 inches deep. That's enough to cover the ground and suppress weeds without the stones shifting underfoot. Go shallower and the landscape fabric shows through; go much deeper and the surface gets awkward to walk on. For larger stone, 3 inches gives fuller coverage.
What is the difference between river rock and gravel?
River rock is naturally rounded and smooth, so it stays loose and won't compact. Crushed gravel has angular edges that lock together and pack down hard, which is why gravel suits driveways and bases while river rock suits decorative beds and drainage. Because river rock doesn't compact, it also tends to roll underfoot on slopes.
Do I need landscape fabric underneath river rock?
Yes, in most beds. A fabric layer keeps the stone from sinking into the soil over time and blocks weeds from rooting up between the rocks. Without it, you'll be topping up material as the rock works its way into the ground and pulling weeds that push through the gaps.
Does wet rock change how much I get per ton?
Yes. Rock bought right after heavy rain carries extra water weight, so a ton of wet material gives you slightly less usable volume than a ton of dry stone. It's a small effect for a decorative bed, but worth knowing if you're ordering by weight after a wet spell.
What size river rock should I use?
Match the size grade to the job. Small stone from 3/8 inch pea gravel up to 3/4 inch suits walkways, play areas, and fine decorative beds; the popular 1 to 3 inch range (including 1, 1 1/2, and 2 inch stone) is the standard for decorative ground cover and most drainage work; and larger 3 to 6 inch stone and cobble armor dry creek beds and slopes for erosion control. Coverage per cubic yard barely changes across sizes, so the calculator works the same whichever grade you pick — the size choice is about how the surface looks and performs, not the amount you order.
Related calculators
Sources
- Gravel Calculator — Material Weights and DensitiesCalculatorSoupPublished density for river rock (2,835 lb/yd³, about 1.42 tons per cubic yard) used to set the working weight-per-yard figure.
- Crushed Stone — Statistics and InformationU.S. Geological Survey (USGS) National Minerals Information CenterAuthoritative material reference for stone used to sanity-check the density range against moisture and geology.
- River Rock — Landscape Materials GlossaryRoseville Rock SupplySupplier reference for the size grades (3/4–1 in, 1–3 in, 3–6 in and cobble) and their typical decorative, drainage, and erosion-control uses.