How to use the rock calculator
- Pick your rock type — river rock, crushed stone, pea gravel or decomposed granite each have a different weight.
- Choose a shape (rectangle, circle, triangle or a ring for a border) and enter the dimensions in feet, inches, yards, metres or centimetres.
- Enter the depth you plan to lay.
- Got more than one area, like a dry creek bed and a border? Press Add another area — they're added together.
- Read the result in cubic yards, cubic feet, tons and bags, tick a waste allowance if you like, and enter a price to see the estimated cost.
Only need the square footage first? Use the square footage calculator, then come back and enter the depth here.
How much rock do I need? The formula
Cubic yards = length (ft) × width (ft) × depth (ft) ÷ 27. Tons = cubic yards × the rock's density.
- Measure length and width in feet, and depth in inches (divide by 12 to get feet).
- Multiply length × width × depth to get cubic feet, then divide by 27 for cubic yards.
- Multiply cubic yards by the density (tons per cubic yard) for the weight.
Worked example: a 30 × 3 ft dry creek bed at 4 in deep, using river rock at 1.33 tons per cubic yard: 30 × 3 × (4 ÷ 12) = 30 cu ft, ÷ 27 = 1.11 cubic yards, × 1.33 = 1.48 tons. Add a 10% settling allowance and that becomes 1.22 cubic yards.
Landscape rock types and recommended depths
| Rock type | Typical density | Recommended depth | Best for |
|---|---|---|---|
| Crushed stone (#57) | 1.4 tons/yd³ | 4–6 in | Driveways, drainage and paths: 4–6 in per compacted layer, 8–12 in total for a new driveway base. |
| Pea gravel | 1.3 tons/yd³ | 2–3 in | Paths, patios and play areas: 2–3 in deep. |
| River rock | 1.33 tons/yd³ | 2–4 in | Decorative beds, dry creek beds and drainage: 2–4 in deep. |
| Decomposed granite | 1.6 tons/yd³ | 2–4 in | Paths and patios, usually compacted in layers: 2–4 in deep, plus extra for compaction. |
Typical, widely published values — actual density depends on moisture and how the rock is laid. Ask your supplier for their exact figure, especially for a paid order.
Rock calculator: tons vs. cubic yards
Suppliers price rock either by the ton or by the cubic yard, and the two describe the same pile of material once you know the density. Denser rock weighs more for the same volume: decomposed granite at 1.6 tons per cubic yard weighs more than pea gravel at 1.3 tons per cubic yard for the same size hole. If a supplier only quotes by the ton, use the calculator's tons figure directly; if they quote by the yard, use the cubic yards figure.
Dry creek beds, borders and ground cover: how deep should rock be?
- Dry creek beds: 2–4 in of river rock, sized to the width of the channel.
- Borders and edging around beds or trees: 2–4 in of river rock, laid over landscape fabric to stop weeds and sinking.
- Decorative ground cover: 2–3 in of pea gravel or decomposed granite, often edged to stop it spreading.
- Drainage areas: 4–6 in of crushed stone, since angular edges lock together and let water pass through.
Border example: a border around a tree bed (6 ft outer diameter, 4 ft inner diameter) at 3 in deep with river rock needs about 0.15 cubic yards (3.93 cu ft) — small enough that bagged rock (about 8 bags at 0.5 cu ft, or 8 bags at 50 lb) can be cheaper than a bulk delivery minimum.
River rock vs. crushed stone vs. pea gravel vs. decomposed granite
River rock is large, rounded and decorative — the classic choice for dry creek beds, borders and accents, at about 1.33 tons/yd³. Crushed stone (#57) is angular and compacts well, making it the right pick for driveways and drainage rather than decorative beds, at 1.4 tons/yd³. Pea gravel is small, rounded and comfortable underfoot, suited to paths, patios and play areas, at 1.3 tons/yd³. Decomposed granite compacts into a firm, natural-looking surface for paths and patios, at 1.6 tons/yd³. Switch the rock type in the calculator above to get the right weight and recommended depth for your project.
Other calculators
- Building a driveway or path instead of a decorative rock bed? Try the gravel calculator.
- Laying mulch around the same beds? Try the mulch calculator.
- Need topsoil for a lawn or raised bed first? Try the topsoil calculator.
- Bedding sand under pavers? Try the sand calculator.
- Just need the area, not the material? Try the square footage calculator.
Frequently asked questions
How much landscape rock do I need?
Multiply the area in square feet by the depth in feet, then divide by 27 to get cubic yards, and multiply by the rock's density to get tons. For a 30 × 3 ft dry creek bed at 4 in deep with river rock (1.33 tons per cubic yard), that's 1.11 cubic yards, or about 1.48 tons. The rock calculator above does this for any shape and depth.
How much river rock do I need for a dry creek bed?
A dry creek bed only needs to be as wide and deep as the water it's meant to channel — most residential ones are 2–4 ft wide and 3–4 in deep in river rock. A 30 ft long, 3 ft wide bed at 4 in deep needs about 1.11 cubic yards (1.48 tons) of river rock. Enter your own length and width as a rectangle in the calculator above.
How much rock do I need for a border around a tree or garden bed?
Choose "Ring / border" as the shape and enter the outer and inner diameters. A border 1 ft wide around a 4 ft diameter tree bed (outer diameter 6 ft, inner diameter 4 ft) at 3 in deep needs about 0.15 cubic yards (3.93 cu ft) of river rock — small enough that bagged rock is often cheaper than a bulk delivery minimum.
What's the difference between river rock, crushed stone, pea gravel and decomposed granite?
River rock is larger, rounded and mostly decorative — dry creek beds, edging and borders. Crushed stone (like #57) has angular edges that lock together under compaction, so it's used for driveways and drainage. Pea gravel is small and rounded, good for paths and play areas. Decomposed granite compacts into a firm, natural-looking surface for paths and patios. Densities differ too: river rock is about 1.33 tons/yd³, crushed stone 1.4, pea gravel 1.3 and decomposed granite 1.6 — switch the rock type in the calculator above to get the right weight.
How deep should landscape rock be?
It depends on the use: decorative ground cover and dry creek beds typically use 2–4 in of river rock, paths and patios use 2–3 in of pea gravel or decomposed granite, and drainage areas or driveways use 4–6 in of crushed stone. Going deeper than needed mostly adds cost without adding function, except where drainage requires the extra depth.
Should I use landscape fabric under rock?
Yes, for most decorative rock beds, dry creek beds and borders — a weed barrier fabric underneath keeps rock from sinking into the soil and cuts down on weeds growing up through it. Skip the fabric only where water needs to soak straight through, like some drainage channels, and check with your supplier or a local extension office for your specific soil and drainage needs.
How many tons of rock do I need?
Tons = cubic yards × the density of the rock you're using. River rock is about 1.33 tons per cubic yard, so the 30 × 3 ft dry creek bed example above (1.11 cu yd) needs roughly 1.48 tons. Densities vary by supplier and by how wet the rock is, so always confirm the exact figure before a paid delivery.
Should I add extra rock for settling or drainage?
Yes — most suppliers recommend an extra 5 to 10% to allow for settling, uneven ground and spillage. Tick "Add a waste / compaction allowance" in the calculator. With a 10% allowance, the dry creek bed example above goes from 1.11 to 1.22 cubic yards.
How do I calculate rock for an irregular bed or ground-cover area?
Split it into simple shapes — rectangles, circles, triangles or a ring for a border — and use "Add another area" in the calculator to add them together. A 12 × 8 ft ground-cover bed at 3 in deep with decomposed granite needs about 0.89 cubic yards (1.42 tons). If you only need the square footage rather than a material estimate, the square footage calculator is a quicker way to measure first.
Is my data saved or sent anywhere?
Your measurements are saved only in your own browser, so they are there next time you open this page on the same device. Nothing is sent to our servers.