Rock & Gravel Calculator

What is a rock and gravel calculator?

A rock and gravel calculator estimates how much crushed stone, pea gravel, or river rock you need for a driveway, path, or drainage bed — in cubic yards, tons, and pounds — based on the area and depth you want to cover.

How this calculator works

• Enter the area length and width in feet and the depth in inches.
• Volume in cubic yards comes from length × width × (depth ÷ 12) ÷ 27.
• Tons are volume × density, with 1.4 tons per yard as the default.
• Adjust the density for heavier (crushed) or lighter (river rock) material.

How to use the result

1. Order the cubic-yard number — that’s how bulk suppliers quote gravel.
2. Use tons to check delivery-vehicle limits and spreading capacity.
3. Match depth to the job: 2–3 inches for paths and mulch-topped beds, 4–6 for driveways.
4. Add 5–10% for compaction and spread loss.

How many tons of gravel do I need?

Multiply your cubic yards by the material’s density — about 1.4 tons per yard for most gravel. A 20×10 ft area at 4 inches is about 2.5 cubic yards, or roughly 3.5 tons. For 100 ft² at 3 inches, figure about 1 cubic yard.

Common mistakes

• Using the wrong depth. A 4-inch driveway and a 2-inch path need twice the difference in material.
• Ignoring density differences. River rock is lighter than crushed stone, so tonnage varies for the same volume.
• Ordering by area instead of volume. Gravel is sold by the cubic yard or ton, never by square footage.

Gravel volume uses the same area–depth math as the mulch calculator — just heavier. If you’re setting posts in the same project, the fence post concrete calculator handles the anchoring material.