How Many Tons of Gravel for a Driveway

There is a unit mismatch at the centre of every aggregate order. You measure a driveway in feet, you specify depth in inches, and the quarry quotes you in tons. Getting from one to the other takes two divisions and a density figure that changes depending on what you are buying.

Work out the tons of gravel correctly and the load arrives right. Get the density step wrong and you can be short by a full ton on a job that looked simple.

The conversion, start to finish

cubic feet  = area (sq ft) × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27
tons        = cubic yards × density

A 40 by 10 foot driveway at 4 inches deep:

• Area: 400 sq ft
• Volume: 400 × (4 ÷ 12) = 133.3 cu ft
• Cubic yards: 133.3 ÷ 27 = 4.94
• Crushed stone at 1.4 tons per yard: 6.9 tons

The 27 comes from a cubic yard being three feet on every side. It is the same divisor used when calculating concrete in cubic yards, and skipping it is the single most common error in material ordering.

Why density is not one number

A cubic yard is a fixed volume. What fills it is not:

Material	Tons per cubic yard
Crushed stone	1.4
Pea gravel	1.3
Sand	1.35
Topsoil	1.1

Swap crushed stone for pea gravel in the identical hole and the tonnage drops about 7%. If you calculate a volume and then order by weight using the wrong density, the truck arrives short and you are paying a second delivery fee to fix a rounding assumption.

The gravel calculator carries these densities and reports both volume and weight, so you can check a supplier's quote against your own measurements before agreeing to anything.

Choose angular stone, not rounded

For a driveway this matters more than the tonnage. Crushed stone has fractured faces that interlock under load and stay where you put them. Pea gravel is rounded, rolls underfoot and migrates — it scatters off the surface and collects at the low end of any slope.

Pea gravel looks better in a photograph and is more comfortable barefoot, which is why it belongs on garden paths and around pools, not under vehicles. If a supplier offers you rounded stone for a driveway, they are selling what is in the yard rather than what the job needs.

The right depth

Depth is where people either overspend or build something that fails in a season:

• 2–3 inches — topping up an existing gravel surface.
• 4 inches — garden paths and walkways.
• 6–8 inches — a driveway carrying passenger vehicles, and normally in two layers: a coarse base course underneath, a finer surface course on top.

A proper driveway is two materials, not one, and each layer is calculated separately. A single 8-inch layer of surface stone is both more expensive and less stable than a graded base with a top course over it.

Compaction: the allowance the formula ignores

The arithmetic above gives you loose volume — material as it sits in the truck. Once it is spread and driven on, aggregate settles.

For a decorative bed that does not matter. For a driveway base it does, and the usual professional allowance is 10 to 20% extra to reach the finished depth after compaction. Skip it and your 6-inch base becomes a 5-inch base within a month of use.

The fees that are not in the per-ton price

Two costs sit outside the quote and surprise people:

Minimum loads. Most yards will not deliver under one or two tons, and many charge for the minimum regardless of what you take. If you need half a ton, bagged stone from a big-box store usually wins once delivery is counted.

Haul fees. Delivery is typically a flat charge based on distance rather than weight. That means the per-ton economics improve sharply with volume — two separate three-ton deliveries can cost meaningfully more than a single six-ton drop. A standard dump truck carries somewhere around 10 to 14 tons, so a large job arrives in multiple loads and the quote should say so explicitly.

There is also a weather effect worth knowing. The densities above are dry-load averages. A load taken after heavy rain weighs several percent more for the same volume, so you are paying for water. It is a small effect, but it is real, and it is one argument for ordering by volume where a supplier permits it.

Checking the quote in ten seconds

The fastest sanity check is coverage per ton. One ton of crushed stone covers roughly:

• 115 sq ft at 2 inches
• 77 sq ft at 3 inches
• 57 sq ft at 4 inches

If a supplier's tonnage implies coverage far from those figures, one of you has the depth wrong — and it is worth resolving before the truck is loaded rather than after it has tipped.

Related calculations

The mulch calculator handles bark and compost, which are sold by volume rather than weight, so no density step is needed. The concrete calculator covers slabs and footings where the same cubic-yard conversion applies. For a patio or path surface over a compacted base, the flooring calculator prices the material going on top.

For technical background on aggregate gradation and base construction, the Federal Highway Administration publishes the specifications state DOTs work from, and your county extension office is usually the best free source on local soil and drainage conditions.