How to calculate how much rock you need
- Find the area: length × width in feet (or use Circle/Triangle for curved beds).
- Multiply by the depth in feet (inches ÷ 12) to get cubic feet; divide by 27 for cubic yards.
- Multiply cubic yards by the rock's weight per yard, then divide by 2,000 for tons.
tons = length (ft) × width (ft) × depth (in) ÷ 324 × lb per yd³ ÷ 2,000
Example: a 6 × 20 ft side strip at 2 inches of pea gravel → 6 × 20 × 2 ÷ 324 = 0.74 yd³ × 2,700 lb ÷ 2,000 =1.0 ton.
How much does a yard of rock weigh?
Most crushed and natural stone weighs 1.3–1.5 tons per cubic yard; lava rock is far lighter. Typical dry weights:
| Rock | Tons per yd³ | 1 ton covers at 2" | 1 ton covers at 3" |
|---|---|---|---|
| River rock | 1.35 (1.25–1.45) | 120 sq ft | 80 sq ft |
| Gravel (general) | 1.4 (1.3–1.5) | 116 sq ft | 77 sq ft |
| Pea gravel | 1.35 (1.25–1.45) | 120 sq ft | 80 sq ft |
| Crushed stone / #57 stone | 1.35 (1.25–1.45) | 120 sq ft | 80 sq ft |
| Crushed limestone | 1.35 (1.25–1.45) | 120 sq ft | 80 sq ft |
| Decomposed granite | 1.4 (1.3–1.5) | 116 sq ft | 77 sq ft |
| Road base / crusher run | 1.5 (1.4–1.6) | 108 sq ft | 72 sq ft |
| Lava rock | 0.55 (0.45–0.75) | 295 sq ft | 196 sq ft |
Wet rock weighs more. Ask your supplier for their weight per yard — the calculator lets you type it in.
How deep should landscape rock be?
- 2 inches for small rock (⅜"–¾") like pea gravel or decomposed granite in beds.
- 3 inches for 1–3" river rock — enough to hide landscape fabric.
- 4–5 inches for larger cobbles (3–5").
- 4–6 inches of compacted road base or crushed stone for a gravel driveway or shed pad, often under 2" of top rock.
FAQ
How many square feet does a ton of river rock cover?
About 120 sq ft at 2 inches deep and 80 sq ft at 3 inches, at 2,700 lb per cubic yard.
Is it cheaper to buy rock by the ton or in bags?
Bulk is much cheaper per ton once you need more than a few hundred pounds. A 0.5 cu ft bag (≈50 lb) at $5–$8 works out to $200–$320 per ton, versus $25–$150 per ton in bulk plus delivery.
How many 50 lb bags of rock make a ton?
40 bags of 50 lb make one ton (2,000 lb).
Should I put landscape fabric under rock?
Under decorative rock, yes — it keeps rock from sinking into the soil and slows weeds. Skip it under mulch-and-rock planting beds you'll replant often.