River Rock Calculator
River rock is smooth, rounded decorative stone (1–3") in mixed earth tones — used for dry creek beds, borders, water features and landscaping. Work out exactly how much you need below.
Sets a typical depth — tweak anything below.
For a 20 ft × 10 ft area at 2 in deep, order about 1.36 cubic yards (1.83 US tons) of river rock.
Estimates only. Densities vary by moisture, compaction and supplier — confirm quantities before ordering.
What is river rock?
River rock is smooth, rounded stone shaped by flowing water, typically 1 to 3 inches across, in mixed earth tones. It's a decorative stone — larger and more polished than pea gravel.
What is river rock used for?
Used for dry creek beds, decorative borders, around plants and downspouts, water features, and erosion control on slopes. It's chosen for looks and durability rather than for compaction or load-bearing.
How much does river rock weigh?
A cubic yard of river rock weighs about 1.35 US tons — roughly 1600 kg/m³, or about 100 lb/ft³. Moisture and compaction shift this, so the calculator applies this density and lets you change it in the extra options if your supplier quotes a different figure.
Coverage by depth
| Depth | Coverage per ton | Coverage per cubic yard |
|---|---|---|
| 1 inch | ~240 sq ft | 324 sq ft |
| 2 inches | ~120 sq ft | 162 sq ft |
| 3 inches | ~80 sq ft | 108 sq ft |
| 4 inches | ~60 sq ft | 81 sq ft |
| 6 inches | ~40 sq ft | 54 sq ft |
Based on about 1600 kg/m³. Actual coverage varies with compaction and moisture.
Common mistakes to avoid
- Guessing the depth. Too shallow and the material shifts and shows the ground beneath. Most surface layers want 2–4 inches; load-bearing bases are built up thicker.
- Forgetting to convert inches to feet. Depth is quoted in inches but volume math is in feet — 4 inches is 0.33 ft, not 4. The calculator handles this, but hand estimates often don't.
- Skipping the waste allowance. Ground is never perfectly flat and material settles once it's placed. Order 5–10% extra so a small shortfall doesn't trigger a second delivery.
- Using the wrong density. Each material weighs differently, so tonnage can be off by 20%+ if you use a generic figure. Pick the right material and adjust the density if your supplier differs.
- Buying bags for a big job. Bagged material costs far more per cubic yard than bulk. Past roughly one cubic yard, a bulk delivery is almost always cheaper.
Frequently asked questions
How deep should river rock be?+
2–3 inches over landscape fabric for decorative beds. Larger 2–3 inch rock is often placed roughly a stone deep; smaller river rock can go a little deeper.
River rock or pea gravel?+
River rock is larger (1–3") and more decorative; pea gravel is small (~3/8") and better for walking on. River rock holds slopes better; pea gravel is comfier underfoot.
Do you need landscape fabric under river rock?+
Yes, in almost every case. River rock is decorative, and you don't want it mixing into the soil or hosting weeds between the stones — woven fabric underneath stops both and keeps the rock easy to clean. Skip fabric only where the rock's job is drainage, like the bed of a dry creek that has to move water.
Will river rock wash away on a slope?+
Large 2–3 inch river rock holds a gentle slope well and is a common erosion fix, but on steeper grades or in a channel that really moves water, stones can shift in a heavy storm. On slopes, use the bigger sizes, set them about a stone deep over fabric, and border the bottom edge so nothing travels off. For a dry creek bed, run larger rock down the center and taper to smaller stone at the banks.