Free Rock Calculator
Use this rock calculator to see how many tons or cubic yards of landscape rock or stone to order for your beds, paths and borders.
Landscape rock and stone are sold by the ton or the cubic yard. This calculator works out the volume from your area and depth, then converts it to tons using a typical weight for the type of rock you choose.
Most rock and stone weighs about 1.3 to 1.5 tons per cubic yard, so a yard of rock is roughly ten times heavier than a yard of mulch.
How much rock do I need? An example
A 15 × 6 ft bed of river rock at 3 in deep: 90 sq ft × 3 in ÷ 12 = 22.5 cu ft, plus 10% extra = 24.8 cu ft. Divide by 27 to get 0.92 cubic yards, or 50 × 0.5 cu ft bags.
How deep should rock be?
| Use | Depth | Notes |
|---|---|---|
| Small decorative rock (up to 1 in) | 2 in | |
| Medium landscape rock (1 to 3 in) | 3 in | |
| Large rock (3 in and up) | 4 in or more | At least as deep as the largest stones. |
| Paths and driveways | 3 to 6 in | Use angular stone that locks together. |
Which rock or stone to use
| Type | Typical size | Best for | Calculator |
|---|---|---|---|
| River rock | ¾ to 3 in, rounded | Beds, borders, dry creek beds | River rock calculator |
| Pea gravel | About ⅜ in, rounded | Paths, patios, play areas | Pea gravel calculator |
| Crushed stone | ¾ to 1½ in, angular | Bases, driveways, drainage | Crushed stone calculator |
| Gravel (mixed) | ¼ to 1 in | Driveways, walkways, ground cover | Gravel calculator |
| Decomposed granite | Fine particles | Compacted paths and patios | Decomposed granite calculator |
Coverage per cubic yard and per bag
| Depth | Sq ft per cubic yard | Sq ft per 0.5 cu ft bag |
|---|---|---|
| 1 in | 324 | 6 |
| 2 in | 162 | 3 |
| 3 in | 108 | 2 |
| 4 in | 81 | 1.5 |
| 6 in | 54 | 1 |
Buying tips
- Round rock (river rock, pea gravel) looks good but rolls under foot. Angular crushed stone packs down firmly for paths and driveways.
- Lay landscape fabric first. Weeds growing through rock are hard to pull out.
- Rock is heavy: a half-ton pickup carries only about half a cubic yard safely, so delivery is usually worth it above a yard or two.
- Decorative rock prices vary widely by colour and source. Enter your supplier's price per yard to see the total.
Frequently asked questions
How much rock do I need?
Multiply length × width (ft) × depth (in) ÷ 12 to get cubic feet, divide by 27 for cubic yards, then multiply by about 1.4 for tons. A 15 × 6 ft bed at 3 in needs 22.5 cu ft (0.83 cubic yards); with 10% extra, order about 0.92 cubic yards, or 1.3 tons.
How many square feet does a ton of rock cover?
About 115 sq ft at 2 in deep, 77 sq ft at 3 in or 58 sq ft at 4 in, for rock weighing about 1.4 tons per cubic yard.
Is this a stone calculator too?
Yes. Choose the type of stone in the calculator. Crushed stone, gravel and decomposed granite are all listed.
How much decorative rock do I need for a flower bed?
At 2 to 3 in deep, each 100 sq ft of bed needs about 0.6 to 0.9 cubic yards of decorative rock, or roughly 0.9 to 1.3 tons.
What depth should landscape rock be?
About 2 in for small decorative rock, 3 in for medium rock and at least the size of the largest stones for big rock, so the ground does not show through.
How accurate is this rock calculator?
The rock calculator gives the exact volume for the measurements you enter, then adds 10% extra (you can change it). Measure carefully: an error of one inch in depth changes a 3 inch layer by a third.
How the rock calculator works
Volume = area × depth. Each area is worked out from its shape (length × width, π × radius², or ½ × base × height), converted to square feet, multiplied by the depth in feet, and added up. Cubic feet ÷ 27 = cubic yards.The extra percentage is then added, and bag counts are rounded up to whole bags. See how we calculate for every figure we use.