How the gravel math works

Area × depth gives the volume: 200 sq ft at 3 in deep is 50 ft³, and ÷27 makes it 1.85 yd³ — the unit bulk gravel is sold in. Ordering by the ton instead? Multiply by the material’s weight per yard. That’s where gravel gets tricky: the volume never changes, but a yard of stone isn’t a fixed weight. Crushed #57 runs ~2,700 lb/yd³, pea gravel ~2,450, crusher run ~3,000, lava rock ~1,500 — the same yard can be anywhere from three quarters of a ton to a ton and a half.

That’s why the density field is a live input, not a hidden constant. The presets are typical industry figures pulled from published supplier tables (all listed on sources); your supplier’s ticket is the real number, and “custom density” takes whatever they quote. The waste margin (default 5%) is applied to the order volume — covering spillage, compaction differences and the tapered ends of a driveway.

Depth quick reference

Use	Typical depth
Decorative top-up over existing gravel	1–2 in
Garden path / walkway	2–4 in
Driveway or parking pad	4–6 in, compacted in lifts
French drain / drainage trench	to pipe depth + cover
Under a paver base	see the paver calculator — base and bedding are separate layers

Bags vs bulk

A 50 lb bag of all-purpose gravel holds ~0.5 ft³, so a cubic yard is ~54 bags. Bagged gravel costs several times the bulk price per yard — it’s for post holes and small patches. Past roughly half a yard, bulk delivery wins; the bag count above shows your crossover. Choosing between #57, crusher run and pea gravel? The gravel types guide covers what each is for, and the mulch and topsoil calculators handle the beds around it.

Frequently asked questions

How do I calculate how much gravel I need?

Area × depth. A 20 × 10 ft parking spot at 3 in deep is 200 × (3 ÷ 12) = 50 ft³ = 1.85 yd³. Weight depends on the stone: crushed stone runs roughly 2,700 lb/yd³, so that's about 1.35 tons per cubic yard — about 2.6 tons with a 5% margin. The calculator above does both as you type.

How much does a cubic yard of gravel weigh?

Roughly 2,400–3,000 lb (1.2–1.5 tons) depending on the material and moisture — crushed stone ~2,700 lb, crusher run ~3,000 lb, lava rock as low as ~1,500 lb. These are typical industry figures, not specs; the ticket at the scale house is authoritative. Every density in this calculator is editable — pick 'custom' if your supplier disagrees.

How much area does a ton of gravel cover?

It depends on depth and density. At ~2,700 lb/yd³ a ton is ~0.74 yd³ = 20 ft³, which covers ~80 sq ft at 3 in or ~120 sq ft at 2 in. Run the exact numbers above — pick your material, set the depth, and read the tonnage off the result.

Is it cheaper to buy gravel by the bag or in bulk?

Bulk, almost always, once you're past a few bags. A 50 lb bag of all-purpose gravel holds ~0.5 ft³, so a cubic yard is ~54 bags — at typical bag prices that's several times the bulk-yard price. Bags make sense for a post hole or a small patch; the bag count above shows exactly where your job lands.

What depth should I use for a gravel driveway or path?

Common practice: 2–3 in for a decorative path refresh, 4 in for a new walkway, 4–6 in (often in two compacted lifts) for driveways and parking. A French drain wants depth to the pipe, not a surface rule. Depth × area is exactly what the calculator computes.

Does the type of gravel change how much I need?

The volume is the same — the weight isn't. A yard of lava rock is ~1,500 lb while crusher run is ~3,000 lb, so tons-per-yard nearly doubles between them. If you're ordering by the ton, material choice changes the count; if ordering by the yard, it doesn't. The gravel types guide has the weight table and what each size is for.