How this river rock calculator works
River rock sells by weight, and the only twist over plain gravel math is depth: rounded stone needs a bed about twice its own diameter or the fabric grins through:
tons = yd³ × 1.35 × (1 + waste%) → rounded up to ¼ ton
At the defaults — a 15 × 10 ft bed, 3 in of 1–3 in rock, 10% allowance — the order is 2.25 tons, about $146 bulk; the full chain is in the load math section below.
River rock sizes and where they go
River rock is smooth, rounded, water-tumbled stone in a range of sizes — the size sets both the look and the depth it needs:
- Pea / small stone (⅜–¾ in) — 1.4 t/yd³: pours smooth, packs a little; paths, containers, and fine ground cover. A 2 in bed hides the fabric.
- River rock (1–3 in) — 1.35: the classic decorative stone for beds, borders and dry creeks. Wants a 3 in bed. The calculator’s default.
- Large cobble (3–5 in): accent stone, dry-creek centers and splash blocks — a 4 in+ bed.
- Never structural: rounded stone can’t lock, so it stays out from under pavers, driveways and anything bearing load — that’s angular crushed-stone work.
For the never-rots, low-maintenance argument against wood, the mulch calculator prices the alternative; for angular structural stone, the gravel calculator.
River rock colors and finishes
Color is regional — river rock is sold as it tumbles out of the wash, so palettes run to the tans, browns, grays and rusts of the local geology, with mixed “rainbow” blends the most common stock. Polished Mexican beach pebble and specialty blacks and whites carry a clear premium over native stone, and darker rock reflects noticeably more heat into the beds around it — worth weighing before you ring a planting with it.
How deep should river rock be?
The rule is simple — about twice the largest stone diameter — because a single layer of rounded rock rolls and shows the ground between pieces:
- ¾ in pebbles: 2 in bed.
- 1–3 in river rock: 3 in bed — the default.
- 3–5 in cobble: 4 in and up.
- Dry creek beds: deeper in the channel center, tapering to the banks.
- Always over woven fabric: it stops the rock sinking into soil and keeps weeding survivable.
How much does a ton of river rock cover?
Coverage per ton by depth — and note the depth is set by stone size, so the practical coverage tracks the rock you choose.
| Depth | Coverage |
|---|---|
| 2 in | ≈ 120 ft² |
| 3 in | ≈ 80 ft² |
| 4 in | ≈ 60 ft² |
| Stone | Bed |
|---|---|
| Pea / ⅜–¾″ | 2″ |
| River rock 1–3″ | 3″ |
| Cobble 3–5″ | 4″+ |
How to measure for river rock
- Measure the bed length and width; pace the curve on island beds and dry creeks, following the shape.
- Set the depth to twice the stone size — 2 in pebbles, 3 in for 1–3 in rock, 4 in cobble.
- Pick the stone size so the density is right — 1.35 for river rock, 1.4 for small stone.
- Leave the allowance at 10% — decorative beds spill and settle a little.
- Enter the per-ton price, delivered — and compare against the bag line, which decorative stone loses past a strip.
Worked example: how much river rock for a 15 × 10 bed
The default, worked line by line — 15 × 10 ft, 3 in of 1–3 in rock at 1.35 t/yd³, 10% allowance, $65 a ton against $7 bags:
volume = 150 × (3 ÷ 12) = 37.5 ft³ = 1.39 yd³
weight = 1.39 × 1.35 = 1.88 → ×1.10 = 2.06 → order 2.25 tons (or 1.75 yd³)
bulk cost = 2.25 × $65 = $146
bag check = (37.5 × 1.1) ÷ 0.5 = 83 bags ≈ $581
The $146-versus-$581 spread is why decorative stone is the classic bulk-delivery win — bags carry a 3–4× premium, and river rock’s premium price makes that gap bite harder than it does on cheap gravel. Past a strip or a couple of containers, order the truck.
What this river rock estimate doesn’t include
River rock is a premium material, so the temptation is to price the stone and forget the bed under it. Fabric and edging aren’t optional on a rock bed — they are what keep it from sinking and spreading — so budget every line below alongside the tons:
- Landscape fabric. Woven geotextile under the rock — commonly $0.15–0.50 per ft², and non-optional.
- Edging. Steel, aluminum or stone to keep rounded rock from migrating into the lawn.
- Delivery. A flat per-load haul fee on a premium-priced material.
- Bed prep. Digging out sod, grading and removing old mulch or rock.
- Drainage work. Pipe and grade for a functional dry creek, not just the look.
- Spreading labor. Placing rounded stone gently over fabric by hand.
River rock FAQ
How much river rock do I need for 150 square feet?
At the typical 3 in depth, a 15 × 10 ft bed takes 2.25 tons (1.39 yd³ exact, ordered as 1.75 yd³ bulk) — about $146 delivered at $65/ton, versus roughly $581 as 83 bags. Bulk wins on anything bigger than a strip.
How many tons of river rock are in a cubic yard?
About 1.35 tons for common 1–3 in river rock, and closer to 1.4 for small ⅜–¾ in stone that packs tighter. Your supplier weighs the load; these figures size the order.
How deep should river rock be?
Twice the diameter of the largest stone: 2 in of depth for ¾ in pebbles, 3 in for 1–3 in rock, 4 in and up for anything fist-sized. Too shallow and the fabric or soil shows; too deep just buries money.
How much does a ton of river rock cover?
About 80 ft² at 3 in deep, 120 ft² at 2 in, and 60 ft² at 4 in. The live coverage line under the drawing tracks your depth and material.
Is river rock better than mulch?
For permanence, yes — river rock never rots, blows away or needs annual topping, so it wins on drainage strips, dry creeks and xeriscapes. Mulch wins in planted beds, because it feeds the soil and holds moisture where roots want it. Rock also reflects heat and is a chore to weed once leaves collect, so match it to the spot.
Should I put landscape fabric under river rock?
Yes — a woven fabric keeps rock from sinking into soil and makes eventual weeding survivable. Overlap seams 6 in, pin it, then place rock gently; skip plastic sheeting, which traps water.
How much does river rock cost?
Commonly $60–130 per ton bulk in 2026 — decorative stone costs multiples of construction gravel, and specialty colors more still — plus delivery. The default bed is about $146 bulk against roughly $581 in bags, the usual decorative bulk-delivery win.
Sources and standards
Decorative stone has no single product spec the way construction aggregate does; the figures here come from landscape practice and the standard estimating densities the whole site shares:
- Standard estimating densities: 1.35 t/yd³ for 1–3 in river rock, 1.4 for small stone — the site-wide aggregate set.
- Landscape practice: the twice-the-stone-diameter depth rule and woven-fabric underlayment.
- Xeriscape guidance: the permanence and heat trade-offs behind the rock-vs-mulch note.
- The scale ticket: supplier weight governs — these figures size the order.
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