Decorative landscape stone
River Rock Calculator
Size decorative river rock and cobble for landscape beds, dry creeks, and borders. Rounded stone is a cover, not a driving surface — this calculator starts at about 100 lb/ft³ and a typical 2-inch bed.
Compaction and waste usually add 5–10%. Densities are bulk, not solid rock. Confirm with your supplier before placing a large order.
0.99 yd³ · 1.33 tons · $73
How to use
Measure the bed, not the whole yard. A dry creek is a winding strip — split it into rectangles, or type the plan’s square footage as a known area. A tree ring or fire-pit surround is a circle. A border along a walk is length times the band width, usually 12–24 inches, not the width of the pavement beside it.
Depth is a decorative layer. Two inches over landscape fabric hides soil in a planting bed. Paths that will be walked on sit closer to three inches so gaps do not show after the cobbles settle. A dry creek that only looks like water is often 3–4 inches of larger stone; if it actually drains, add a deeper drainage-stone trench as a second area. Keep six-inch driveway depths for angular crushed stone — rounded river rock rolls under tires.
The calculator starts at about 100 lb/ft³ for mixed 1–3 inch landscape cobble. You are buying coverage, not a compacted base: rounds do not lock like crushed driveway mix. If the quarry ticket lists tons per yard or a different density, type that number. Optional bag size and unit price are useful for a short border; bulk by the ton or the yard is cheaper once you need about a cubic yard.
How deep to lay river rock
Formulas
Coverage uses the same volume math as the gravel calculator, with a lighter bulk density for rounded cobble:
cubic feet = area (sq ft) × (depth in inches ÷ 12) cubic yards = cubic feet ÷ 27 tons = (cubic feet × density lb/ft³) ÷ 2,000
The sample 20×8 ft bed at 2 inches is 160 sq ft → 0.99 yd³ and 1.33 tons at 100 lb/ft³. For cubic-yard worked examples, circles, and metric conversion, use the full gravel formula explainer on the homepage.
River rock vs pea gravel vs crushed stone
Use this page when you are ordering rounded landscape cobble. Switch the preset or open the Gravel calculator for a driveway, compacted path base, or drainage fill. For pea gravel, lava rock, or marble chips in a bed or path, open the Rock calculator.
What each mix looks like
| Material | Feel | Density used | Best for |
|---|---|---|---|
| River rock | Rounded cobble, often 1–3 in | 100 lb/ft³ (1.35 t/yd³) | Beds, borders, dry creeks, decorative river stone |
| Pea gravel | Small smooth 3/8 in stones | 105 lb/ft³ (1.42 t/yd³) | Garden paths and play areas |
| Crushed stone | Angular rock that locks | 110 lb/ft³ (1.49 t/yd³) | Driveways, patio bases, compacted layers |
Landscape river rock — also sold as decorative river stone or mixed cobble — is water-worn. The stones are larger and smoother than pea gravel. A pile looks heavy, but the voids between round pieces mean a cubic foot is often a bit lighter than crushed stone. This calculator uses 100 lb/ft³ (about 1,600 kg/m³), or 1.35 tons per cubic yard. If your yard lists 1.3 or 1.4 tons per yard, type their number.
Pea gravel is the small cousin: better underfoot, typically around 105 lb/ft³, still prone to migrating on slopes. Choose it for a walking surface. Choose river rock when you want a visible cobble bed, a dry creek, or a border that reads as stone rather than as a fine path mix. Plan an edge restraint either way.
Crushed stone belongs under tires and in compacted bases. Rounded cobble does not lock, so order for coverage and add 5–10% for uneven ground, fabric wrinkles, and hungry edges. Confirm color and size before the truck is loaded — decorative mixes vary more than crushed driveway stone.