How to use the landscape rock calculator
- Choose the shape. Rectangle, circle, several parts for L-shapes and curves, or type in the area if you already know it.
- Enter the size and depth. Length and width in feet; depth in inches. Feet and inches like 12' 6" work too.
- Read the result in cubic yards, tons and bags. Under Adjust assumptions you can change the weight per yard, extra and bag size.
- Add your supplier's price per ton, yard or bag to see the cost, including delivery.
The landscape rock formula
Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet × (1 + extra) ÷ 27
Tons = cubic yards × weight per cubic yard
Bags = cubic feet with extra ÷ bag size, rounded up
Worked example
A 15 × 10 ft rock bed, 2 inches deep
- 150 sq ft × (2 ÷ 12) = 25 cu ft; with 5% = 26.3 cu ft.
- 26.3 ÷ 27 = 0.97 cubic yards.
- At about 1.35 tons per yard: 1.31 tons.
How far a cubic yard goes
| Depth | One cubic yard covers | 0.5 cu ft bags per 10 sq ft |
|---|---|---|
| 1 in | 324 sq ft | 1.7 |
| 2 in | 162 sq ft | 3.3 |
| 3 in | 108 sq ft | 5.0 |
| 4 in | 81 sq ft | 6.7 |
| 6 in | 54 sq ft | 10.0 |
A cubic yard is 27 cubic feet, or 54 bags of 0.5 cu ft.
Approximate weights per cubic yard
- Decorative stone, crushed granite: 1.3 to 1.5 tons.
- Pea gravel: about 1.4 tons.
- Lava rock: 0.5 to 0.8 tons.
- Marble chips: about 1.4 tons.
Common mistakes to avoid
- Using gravel weight for lava rock. Lava rock is about half the weight; you would over-order by tons.
- No fabric or edging. Rock sinks and spreads without them.
- Too deep around plants. Keep rock back from stems to avoid heat damage.
- Forgetting delivery limits. Check whether the truck can reach your drop spot.
Frequently asked questions
How much landscape rock do I need?
Multiply the bed area by the depth in inches and divide by 324 for cubic yards, then multiply by the weight per yard for tons. 150 sq ft at 2 inches is 0.93 cubic yards, about 1.25 tons.
How much does landscape rock weigh?
Most decorative stone weighs 1.3 to 1.5 tons per cubic yard. Lava rock is much lighter, about 0.5 to 0.8 tons per yard, so a ton covers far more area. Change the weight under Adjust assumptions.
How deep should decorative rock be?
About 2 inches for small rock and 3 inches for larger stone, enough to hide the fabric underneath.
How much does a ton of rock cover?
At 1.35 tons per yard and 2 inches deep, one ton covers about 120 sq ft.
Rock or mulch?
Rock lasts for years and does not blow away, but it heats up in sun and is hard to change later. Mulch feeds the soil and suits planted beds better.