Gravel & Stone Calculator

How this calculation works

Cubic yards = (area in sq ft x depth in inches / 12) / 27, the same base formula as mulch and soil. Tons = cubic yards x density factor, where density varies by stone type — crushed stone typically runs heavier per cubic yard than river rock of the same volume, and decomposed granite (finer, more compactable) sits somewhere in between depending on moisture content. Always check the specific supplier's tons-per-yard figure for the exact product, since it varies by quarry and stone size, not just broad category.

Depth needed varies hugely by use: a walkway base might only need 2-3 inches of compacted gravel, while a driveway base commonly needs 4-6 inches (sometimes in two compacted lifts) to support vehicle weight, and a drainage bed around a downspout or French drain often needs a deeper, more open-graded stone.

Common mistakes

• Using one flat tons-per-yard conversion for every stone type, which under- or over-orders depending on whether the actual material is heavier or lighter than assumed.
• Skipping compaction — loose gravel settles noticeably once compacted or driven over, so a driveway base spec often calls for slightly more raw material than the finished depth alone suggests, laid and compacted in lifts.
• Using the wrong depth for the application — a walkway's 2-3 inch depth won't support a driveway's vehicle loads.
• Not checking delivery truck weight limits on large orders, which can force a split delivery if tonnage is underestimated.
• Choosing an open-graded (large, uniform stone) product for a compacted base application, or vice versa — base material needs a mix of stone sizes to compact densely, while drainage stone needs the opposite (uniform, open gaps), and using the wrong one undermines the project's actual purpose.
• Not accounting for edging or a border to contain the gravel, which can migrate and thin out over time on an open-edged bed or path without one.

Shopping summary

Order by the ton (bulk suppliers typically price and deliver by weight) using your stone type's actual density figure, rounded up from calculated cubic yards, at the depth appropriate to your specific project (walkway, driveway base, or drainage bed).

Worked example: a 20x30 foot driveway base at 5 inches depth needs (600 x 5/12)/27 ≈ 9.26 cubic yards. At roughly 1.4 tons per cubic yard for crushed stone, that's about 13 tons — a large enough order that most suppliers deliver by dump truck rather than bagged, and worth confirming the truck's access to your driveway before scheduling.

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