A ton of river rock covers about 75 to 85 square feet at 3 inches deep, or 115 to 125 square feet at 2 inches, for the common 1–2 inch size. Larger stone has to be laid deeper, so a ton of 4–8 inch rock covers only about 68 square feet at its minimum 4-inch depth. Coverage per ton depends on both the rock size and the depth you spread it — the table below gives every combination.
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| Rock size | Density (tons/yd³) | 2″ deep | 3″ deep | 4″ deep | 6″ deep |
|---|---|---|---|---|---|
| 3/8″ pea-sized | 1.40 | 116 sq ft | 77 sq ft | 58 sq ft | 39 sq ft |
| 1″–2″ small | 1.30 | 125 sq ft | 83 sq ft | 62 sq ft | 42 sq ft |
| 2″–4″ medium | 1.25 | — | 86 sq ft | 65 sq ft | 43 sq ft |
| 4″–8″ large | 1.20 | — | — | 68 sq ft | 45 sq ft |
A dash means the depth is shallower than the stones themselves — you cannot lay 4-inch rock 2 inches deep. Figures are for dry material; wet or muddy rock weighs more per yard and covers slightly less per ton.
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A cubic yard is a fixed volume — 27 cubic feet — so a yard covers 162 sq ft at 2 inches, 108 at 3 inches, and 81 at 4 inches no matter what stone you use. A ton is a fixed weight, and how much volume a ton fills depends on density. Small stone packs tighter, so a ton of pea rock is only 0.71 cubic yards; a ton of 4–8 inch cobbles, with bigger gaps between the stones, is 0.83 cubic yards.
That produces a counterintuitive result: at the same depth, a ton of large rock covers more area than a ton of small rock. But large rock cannot be laid at the same depth — it needs at least 4 inches to sit properly — so in practice a ton of large rock covers less ground and costs more per square foot. If you are choosing a size on budget alone, smaller stone laid shallow is the cheapest way to cover an area.
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Say a supplier delivers 2 tons of 1–2 inch river rock and you plan a 3-inch layer. From the table, one ton covers about 83 sq ft at 3 inches, so 2 tons covers roughly 165 square feet — a bed about 16 ft by 10 ft. Spread it 2 inches instead and the same 2 tons stretches to about 250 sq ft, but small stone at 2 inches shows soil through in places once it settles, so 3 inches is the safer depth for a bed you want to look finished.
Going the other direction — starting from your area and working out the tons — is what the river rock calculator does, including the density for each size so you do not have to look it up.
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Suppliers sell by the half ton, so round up. Add about 10% for settling and uneven ground; on a 2-ton estimate that means ordering 2.5 tons rather than risking a second delivery fee for a small top-up. And ask which size class their tons-per-yard figure is based on — the difference between 1.20 and 1.40 tons per yard is 17% on your coverage, which is the gap between finishing the bed and running short on the last strip.
For weight rather than coverage, see how much a yard of river rock weighs. Comparing stone types? Crushed stone is denser, so how much a ton of gravel covers works out slightly lower than river rock at the same depth.