River rock: How Deep and How Much
Published density and depth figures for river rock, each with its source shown — where sources disagree, we list both instead of averaging. All sources also on the methodology page.
Density (as published)
| As stated | Density | Source |
|---|---|---|
| River Rock | 2,835 lb/cu yd | CalculatorSoup Gravel Calculator density table |
| Rock (2-6") | 3,200 lb/cu yd | TRORC Material Weight Chart |
| Multi Colored River Rock (3-5") | 2,410 lb/cu yd | GravelShop.com product calculator |
How deep
| Use | Depth | Source |
|---|---|---|
| walkway/path | 3–4 in | HomeToSight - How Deep Should Landscape Rock Be |
| driveway | 4 in | HomeToSight - How Deep Should Landscape Rock Be |
| drainage/dry creek bed | 3–4 in | HomeToSight - How Deep Should Landscape Rock Be |
| decorative/flower bed | 2–3 in | HomeToSight - How Deep Should Landscape Rock Be |
| walkway/path, small river rock size-specific | 2.5–3 in | HomeToSight - How Deep Should Landscape Rock Be |
| walkway/path, medium river rock size-specific | 3–4 in | HomeToSight - How Deep Should Landscape Rock Be |
A 100 sq ft area at 3.5 inches needs about 1.08 cubic yards — 1.30 to 1.73 tons depending on which cited density you use. Formula: sq ft × depth ÷ 324; tons = yards × density ÷ 2,000.
Run your own dimensions through the gravel calculator
How rounded materials behave
Rounded materials, such as pea gravel and river rock, form through water action rather than mechanical crushing. UC ANR (UC Master Gardener) gives pea gravel as its example of "river-run" gravel: it never packs down completely, and the rounded pieces slip and slide underfoot, which makes it hard to walk on or to set furniture on. River rock behaves the same way in UC ANR's guidance, staying loose unless large stones are worked in to give it support.
Because rounded gravel doesn't lock together, it spreads. UC ANR recommends an edging border, using bender board, plastic edging, rock, pavers, brick, or lumber, to keep pea gravel and river rock from migrating into the soil beside a bed or path.
That loose behavior steers rounded gravel toward decorative beds, ground cover, and drainage features rather than hard-traffic paths. HomeToSight lists 2 to 2.5 inches for a pea gravel mulch bed and 2 to 3 inches for a river rock flower bed. For a dry creek bed or other drainage feature, HomeToSight calls for 3 to 4 inches of river rock, the same range it gives for a river rock walkway, and 4 inches or more for a river rock driveway. UC ANR's own walkway figure for gravel generally is a 2-inch practical minimum, extended to 4 inches where thicker stones or pavers are worked in.
What the sources say
- River-run rock never packs down completely into a solid surface; pieces slip and slide, making it difficult to walk on or place furniture on. Works for paths/patios only if large stones are incorporated to support furniture; otherwise better suited as mulch/ground cover. (UC ANR)
Common questions
How many tons is a cubic yard of river rock?
1.21 to 1.60 tons per cubic yard across the cited figures above. Suppliers weigh loads at the scale, so their ticket beats any table.
Why do the density figures disagree?
Moisture, stone size, and compaction all move the number, and some retail calculators reuse one site-wide default. We show each source's figure with attribution so you can see which kind of source it is.
Planning estimates from the cited figures, as of 2026-07-13. Your supplier's scale ticket and your soil conditions decide the real number.