Gravel Calculator: How Much Gravel Do I Need?

The Formula

Length (ft) x Width (ft) x Depth (inches) / 324 = Cubic Yards

Suppliers sell gravel two ways: by the cubic yard and by the ton. You need both numbers because the price sheet might list one and the delivery ticket lists the other.

Cubic Yards to Tons

Gravel weighs roughly 1.4 tons per cubic yard. That number changes with the type:

• Crushed limestone: 1.35 tons/yd
• Pea gravel: 1.35 tons/yd
• Crusher run (3/4” minus): 1.5 tons/yd
• River rock: 1.35 tons/yd
• #57 stone: 1.4 tons/yd
• Decomposed granite: 1.6 tons/yd

Wet gravel is heavier. If it rained last night and the yard is loading from an outdoor pile, your load will weigh 10-15% more than the dry weight. You’re paying by the ton, so you’re paying for water. Ask if they have covered stockpiles.

Driveway Example

A single-lane driveway: 12 feet wide, 60 feet long, 4 inches deep.

12 x 60 x 4 / 324 = 8.89 cubic yards

At 1.5 tons per yard for crusher run: 13.3 tons.

But that’s the installed depth. You need to account for compaction.

The Compaction Factor

Loose gravel compacts 15-20% when you run a plate compactor or roller over it. A 4-inch finished depth requires about 4.8 inches of loose gravel.

For our driveway: 12 x 60 x 4.8 / 324 = 10.67 cubic yards. At 1.5 tons/yd: 16 tons.

The difference between skipping compaction factor and accounting for it is 2.7 tons. At $35/ton delivered, that’s $94. Order short and you’re making a second trip to the quarry or paying another $75 delivery fee.

Not all applications need compaction. Decorative gravel in a garden bed sits loose. Driveway base, French drain backfill, and paver sub-base all get compacted. If a compactor touches it, add the 20%.

Depth by Application

Different jobs call for different depths.

Driveway base (crusher run): 4-6 inches compacted. Six is better if your soil is clay. Clay holds water, water softens the base, and your gravel sinks into the mud. Ask anyone with a gravel driveway on red clay how many times they’ve had to add stone.

Paver sub-base: 4-6 inches of compacted #57 or crusher run, then 1 inch of bedding sand. The Interlocking Concrete Pavement Institute (ICPI) recommends a minimum 4 inches for pedestrian areas and 6-8 inches for vehicular.

French drain backfill: Fill the trench with 3/4” clean stone (no fines) around the perforated pipe. The stone should extend from 2 inches below the pipe to 2 inches above it at minimum, though most contractors fill within 6-8 inches of grade.

Walkway or garden path: 2-3 inches of pea gravel or decomposed granite over landscape fabric. No compaction needed. These settle on their own.

Shed foundation pad: 4 inches of compacted crusher run, leveled. For a 10 x 12 shed: 10 x 12 x 4.8 / 324 = 1.78 yards. Two yards.

Driveways: The Real Math

Gravel driveways should be built in layers. The standard cross-section:

Bottom: 4 inches of large stone (2-4” rock) for stability on soft subgrade. Middle: 4 inches of #57 stone (3/4” clean). Top: 2 inches of crusher run (3/4” minus with fines) that compacts into a hard surface.

That’s 10 inches total loose depth across three lifts. For a 12 x 60 driveway:

12 x 60 x 10 / 324 = 22.2 cubic yards total across all three layers.

At $30-40/ton delivered, a proper three-layer gravel driveway for a 60-foot single lane runs $900-$1,250 in stone. Not cheap. A lot of people pour 4 inches of crusher run directly on native soil and call it done. It works for a year or two, then the gravel migrates into soft spots and you’re adding more stone.

The Delivery Question

A tandem dump truck carries 12-15 tons (about 8-10 cubic yards). A tri-axle carries 22-25 tons. Our 16-ton driveway order fits in one tri-axle load.

Delivery is typically $50-100 within 20 miles of the quarry. Some suppliers include delivery over a minimum order (usually 10+ tons). Below that minimum, the delivery fee is sometimes more than the stone.

If you have a pickup truck and the quarry is close, you can haul it yourself. But a cubic yard of gravel weighs 2,800 pounds, and a half-ton truck’s payload maxes at 1,500-2,000 pounds. You’d need 10+ trips for a driveway. Pay the delivery fee.

Common Mistakes

Using the wrong stone for the job. Pea gravel on a driveway looks nice for a week, then displaces under tires and rolls into the yard. River rock in a French drain clogs with sediment because the rounded stones don’t lock together. Crusher run on a garden path tracks into the house on shoes.

Not accounting for edge spillage. Gravel without borders (edging, timber, or stone) spreads outward over time. A 12-foot driveway with no edging effectively becomes 14 feet wide within two years, thinning the depth in the center. Either install edging or order 10% extra to compensate for migration.

Running the Numbers

SiteCalc has calculators for gravel, mulch, and topsoil that handle cubic yards, tonnage, compaction factor, and cost. Pick the material type, enter dimensions and depth, and it gives you yards, tons, and total cost. The budget calculator runs the math backward if you’re working from a dollar amount instead of a measurement.

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