What Is a Gravel Calculator?

Gravel is measured in one unit and sold in another. You plan a driveway or path in square feet and inches of depth, but the quarry weighs your truck and charges by the ton. A gravel calculator bridges the two: it turns length, width, and depth into cubic yards of volume, then multiplies by the density of the specific stone you picked to get tons to order. That last step matters more than people expect — a yard of light, rounded pea gravel and a yard of dense decomposed granite differ by a quarter ton, so “three yards of gravel” is not one number on the scale ticket.

How It Works

First the footprint and depth become a volume, with depth converted from inches to feet:

Then volume becomes weight using a typical dry density for the material — crushed stone 1.4, pea gravel 1.35, river rock 1.5, and decomposed granite 1.6 tons per cubic yard:

Worked Example: A 20 × 10 ft Pad, 4 Inches Deep

A 20 × 10 ft parking pad covers 200 sq ft. At 4 inches deep, that is 200 × (4 ÷ 12) = 66.7 cubic feet, or 66.7 ÷ 27 = 2.47 cubic yards. In crushed stone at 1.4 tons per yard, the order is 2.47 × 1.4 = 3.46 tons. These are the calculator’s default inputs, so the breakdown shows the same chain on load. The same volume in bagged gravel would be 134 half-cubic-foot bags — roughly 6,700 pounds hauled fifty pounds at a time, which is why anything beyond a small path goes bulk.

Compaction and Base Layers

The calculator gives you the volume of the finished layer — but gravel that gets compacted does not stay at its delivered volume. Run a plate compactor over a fresh lift of crushed stone and it consolidates by roughly 10–15% as the angular pieces lock together and the voids close. If you are building a structural base — under a shed, a paver patio, or a driveway — order that much extra so you still finish at your target depth after compaction. Deep bases should also go down in lifts: compact every 2–3 inches rather than trying to compact 6 inches at once, which only firms up the top. Note the difference by material: crushed stone and decomposed granite compact and lock; rounded pea gravel and river rock never really do, which is why they belong on top as a decorative layer, not underneath anything that needs to stay put.

Common Mistakes to Avoid

The most expensive mistake is ordering by yards when the supplier quotes tons, or vice versa, without checking the conversion — densities on quarry tickets range from about 1.2 to 1.7 tons per yard depending on stone and moisture, so confirm the figure on your quote rather than assuming. Second is skimping on depth: 2 inches of loose gravel on bare soil disappears into mud within a season; paths want 3–4 inches over a compacted base, and driveways want 6–8 inches total, laid in lifts. Third is skipping the compaction allowance on base work and coming up short after the plate compactor does its job. Finally, don’t lay gravel straight onto soft ground — a woven geotextile fabric under the stone keeps it from migrating downward and can halve how often you top up.

Frequently Asked Questions