Rock calculator
Cubic yards and tons of river rock, crushed stone or lava rock for a bed or a border.
A 20 × 5 ft bed 3 in deep needs 0.93 cubic yards of river rock, about 1.31 tons.
Measure
You need
about 1.31 tons · 25.0 ft³ · 0.71 m³
Your shopping list
Priced by the ton
1.31 tonst
Short tons of 2,000 lb
Priced by the yard
0.93 yd³m³
Loose cubic yards
Type a price per ton and a price per cubic yard to see which quote is cheaper.
Everything is calculated in your browser. Nothing you type is sent anywhere.
How it is calculated
- Area20 ft × 5 ft = 100 ft²
- Volume100 ft² × 3/12 ft = 25.0 ft³
- Cubic yards25.0 ÷ 27 = 0.93 yd³
- Tons0.93 × 1.42 = 1.31 tons
Rock for a 100 ft² bed
100 ft² is 0.62 yd³ at 2 in and 0.93 yd³ at 3 in.
| Rock | Tons per yd³ | Tons at 2 in | Tons at 3 in |
|---|---|---|---|
| Gravel (¼ to 2 in) | 1.42 | 0.88 | 1.31 |
| Crushed limestone | 1.30 | 0.80 | 1.20 |
| Base course | 1.25 | 0.77 | 1.16 |
| Riprap | 1.05 | 0.65 | 0.97 |
| Lava rock (scoria) | 0.48 | 0.29 | 0.44 |
What one ton covers
| Rock | ft² at 2 in | ft² at 3 in |
|---|---|---|
| Gravel (¼ to 2 in) | 114 | 76 |
| Crushed limestone | 125 | 83 |
| Base course | 130 | 86 |
| Riprap | 154 | 103 |
| Lava rock (scoria) | 341 | 227 |
Rock for common beds, 3 in deep
| Bed | yd³ | Tons, river rock | Tons, lava rock |
|---|---|---|---|
| 3 × 10 ft | 0.28 | 0.39 | 0.13 |
| 4 × 8 ft | 0.30 | 0.42 | 0.14 |
| 4 × 20 ft | 0.74 | 1.05 | 0.35 |
| 5 × 20 ft | 0.93 | 1.31 | 0.44 |
| 10 × 10 ft | 0.93 | 1.31 | 0.44 |
| 4 × 40 ft | 1.48 | 2.10 | 0.70 |
| 10 × 20 ft | 1.85 | 2.63 | 0.88 |
| 20 × 20 ft | 3.70 | 5.26 | 1.76 |
Frequently asked questions
How much does a yard of river rock weigh?
About 1.42 short tons, or 2,840 lb, for loose rock ¼ to 2 inches. Bigger cobbles leave more air between stones: ask your supplier for their weight per yard and type it in "Tons per cubic yard".
How much area does a ton of river rock cover?
About 114 ft² at 2 inches deep and 76 ft² at 3 inches. A ton of lava rock covers 227 ft² at 3 inches, because it weighs a third as much.
How deep should landscape rock be?
2 to 3 inches for rock, gravel, lava rock and other inorganic mulch, against 3 to 4 inches for wood mulch (Utah State University Extension). Lay landscape fabric first if you want fewer weeds.
How much rock do I need for a 10 × 10 bed?
At 3 inches deep, 100 ft² takes 0.93 cubic yards: about 1.31 tons of river rock, 1.20 tons of crushed stone or 0.44 tons of lava rock.
Should I buy lava rock by the ton or by the yard?
Lava rock (scoria) weighs about 0.48 tons per cubic yard against 1.42 for river rock, so a ton of it fills 2.11 yd³. Type both prices in the calculator: it converts your bed to tons and yards and shows which quote is cheaper.