Landscape rock calculator: rock types compared
The kind of rock changes the weight far more than the volume: a cubic yard of river rock or crushed stone weighs about 2,700–3,100 lb, while lava rock (cinders) weighs only 800–1,200 lb.[1] So order by the cubic yard when comparing rocks, and by weight only once you know which rock it is.
| Rock | lb per cubic yard | Cubic yards per ton | Sq ft per ton at 2 in |
|---|---|---|---|
| River rock, gravel, crushed stone | 2,700–3,100 | 0.64–0.74 | 104–120 |
| Lava rock (cinders) | 800–1,200 | 1.67–2.5 | 271–405 |
Decorative rock sold by size names (pebbles, cobbles) is still loose stone in this range; weigh one bag or ask the supplier for its weight per yard if it differs.
Square feet covered by one ton
One US ton of river rock covers about 70–80 sq ft at 3 inches deep.
River rock is usually priced per ton, so the useful question is how far a ton goes. One ton is about 0.64–0.74 cubic yards of loose stone, using the general gravel weight range of 2,700–3,100 lb per cubic yard.[1]
| Depth | Square feet | Square meters |
|---|---|---|
| 2 in | 104–120 | 9.7–11.2 |
| 3 in | 70–80 | 6.5–7.4 |
| 4 in | 52–60 | 4.9–5.6 |
| 6 in | 35–40 | 3.2–3.7 |
We found no primary source with a density specific to river rock, so these figures use the gravel range. Large, rounded stones leave bigger gaps, so a real ton may cover a little more or less. If your supplier quotes another material by the ton, the tons to cubic yards converter covers it.
How deep should river rock be?
At least as deep as the stones are wide; small stone used as a mulch goes 2–3 inches deep.
Published guidance treats small stone as a mulch: Utah State recommends 2–3 inches of inorganic mulch such as rock or gravel.[2] Colorado State notes that stones larger than about half an inch do not work well as a mulch,[3] so river rock, which is usually larger, is mainly decorative. For a stone mulch, pea gravel or another small gravel fits that guidance better, and the gravel depth guide lists depths for paths and mulch.
For decorative cover the practical limit is geometry: a layer cannot be thinner than one stone. Measure a few typical stones and make the depth at least that, or a little more so the ground does not show between them. There is no published standard for this, so treat it as a starting point.
Dry creek bedsMeasure the channel as a long rectangle (average width × length) or split curves into parts, as shown in measuring irregular areas. Enter the depth of stone you will place, not the depth of the excavated channel.
2 inch river rock: depth and coverage
Stones about 2 inches across need a layer at least 2 inches deep, and a little more hides the soil between them. At 2 inches one US ton covers about 104–120 sq ft; at 3 inches, about 70–80 sq ft. Enter your depth in the calculator for cubic yards and tons.
River rock sizes
There is no standard river rock size, so compare your supplier's range with the AASHTO sizes below.
Landscape suppliers sell river rock by their own size names, so check the actual range. For reference, the standard AASHTO aggregate sizes run from #1 (about 4 in to ¾ in) and #3 (about 2½ in to ½ in) down to #57 (about 1 in to 3/16 in).[4] The RHS describes chunkier gravel grades as 20 mm or more.[6]
Bagged river rock
Small river pebbles are sold in 0.5 cu ft bags by at least one major manufacturer,[5] 54 bags to the cubic yard. Larger rock is generally sold loose by weight. For crushed, angular stone, use the gravel calculator instead.
Yards and tons for common beds
A 30 × 3 ft border 4 inches deep needs 1.11 cubic yards, about 1.5–1.7 tons.
| Bed (ft) | At 3 in | At 4 in | At 6 in |
|---|---|---|---|
| 30 × 3 | 0.83 yd³ (1.1–1.3 t) | 1.11 yd³ (1.5–1.7 t) | 1.67 yd³ (2.2–2.6 t) |
| 20 × 5 | 0.93 yd³ (1.2–1.4 t) | 1.23 yd³ (1.7–1.9 t) | 1.85 yd³ (2.5–2.9 t) |
| 10 × 20 | 1.85 yd³ (2.5–2.9 t) | 2.47 yd³ (3.3–3.8 t) | 3.7 yd³ (5–5.7 t) |
| 40 × 4 | 1.48 yd³ (2–2.3 t) | 1.98 yd³ (2.7–3.1 t) | 2.96 yd³ (4–4.6 t) |
Frequently asked questions
How much river rock do I need?
Square feet × depth in inches ÷ 324 = cubic yards. Multiply by about 1.35–1.55 for US tons. A 30 × 3 ft border at 4 inches is 1.11 yd³, about 1.5–1.7 tons.
How many square feet does a ton of river rock cover?
About 104–120 sq ft at 2 inches and 52–60 sq ft at 4 inches.
How deep should river rock be?
At least one stone deep. For small stone used as mulch, Utah State suggests 2–3 inches.[2]
How much does a yard of rock weigh?
Loose stone such as gravel or river rock weighs about 2,700–3,100 lb per cubic yard (1.35–1.55 US tons).[1] Solid, unbroken rock is much heavier, because there are no gaps between pieces.
How much does a yard of river rock weigh?
Using the loose gravel range, about 2,700–3,100 lb (1.35–1.55 US tons).[1]