How Much Gravel Do I Need?

Ask which unit before you say a number

A 40 × 12 driveway at 4 inches deep needs:

5.93 cubic yards — or 8.3 tons.

Same pile. And bulk suppliers are genuinely split on which they price by.

Say "6" to a yard that sells by weight and you're 28% short. Say "8" to one that sells by volume and you're 35% over, on a delivery that can't go back.

That's the single most expensive mistake available on this page, and it's avoided by one question.

The arithmetic

Enter the length and width of the area and the depth in inches. The depth divides by 12 to convert to feet, and everything else is a straight multiplication:

40 × 12 × (4 ÷ 12) = 160 cubic feet

160 ÷ 27 = 5.93 cubic yards

5.93 × 1.4 tons per yard = 8.30 tons

Density is a range, not a constant

Which is why the calculator asks rather than assuming.

Material state	Tons per cubic yard
Loose crushed gravel	1.35 – 1.5
Some crushed stone	up to 1.7
Compacted	around 1.55

A 20% difference in density is a 20% difference in your bill — far too large to guess at. Ask your supplier for the figure for the material you're actually buying, not a general one.

Depth is where people under-order

Four inches is the common figure for a driveway surface course, and that's what most people price.

But a driveway built properly is several layers — a coarser base beneath the top course — so the total excavation is considerably deeper than the layer you're calculating. If you're building from scratch rather than topping up, work out each layer separately.

A path or decorative bed is fine much shallower, often around 2 inches.

Gravel settles

A loose-dumped layer compacts under traffic, so a driveway finished exactly to depth on day one will sit noticeably low within a season.

Ordering slightly over, or planning to top up after a few weeks once it's bedded in, is normal practice rather than a mistake. Bulk deliveries tend to come in fixed increments anyway.

The thing that isn't gravel but saves the most gravel

Geotextile fabric underneath.

It stops the stone migrating down into the soil — which is how a gravel drive quietly disappears over a few years and needs topping up again and again. It isn't in this calculation and it's far cheaper than the stone it saves.

Edging does the same job sideways, stopping the gravel travelling into the lawn.

Look at the pounds figure before planning the labour

16,593 lb, on the default job.

A loaded wheelbarrow is roughly 300 pounds. The distance from where the lorry can tip to where the gravel actually needs to be is the number that decides whether this is an afternoon or a weekend — and it's worth working out before the delivery arrives, not after.

Also worth checking before then: whether the tipper can get in at all, and whether there's somewhere it can dump that isn't where the gravel has to end up.

Irregular areas

Measure as several rectangles and add the volumes. Don't use the bounding box of an L-shape — it includes ground you're not covering.

For a curved edge, measure the containing rectangle and accept a small over-order. Gravel tolerates that better than most materials, because surplus is easy to spread somewhere else.

Print the aggregate order sheet — the first line on it is which unit your supplier sells by, because everything else depends on that answer.

Sources: Inch Calculator — gravel · Select SG — how much a yard of crushed stone weighs