Gravel Calculator — Cubic Yards, Tons and Cost

Work out how much gravel a driveway, path or landscaping project needs — in cubic yards, tons or cubic metres, how many bags that is, and what the material will cost. Handles rectangles, circles, triangles and several areas at once, for pea gravel, crushed stone, river rock and limestone.

Created by Ashar PervaizLast updated 24 October 2026

How Much Gravel Do I Need for a Driveway?

Three numbers decide it: how long the drive is, how wide, and how deep you want the stone. Length times width gives the area, and area times depth gives a volume — the only trick is that depth is usually quoted in inches while the other two are in feet, so one of them has to be converted before they can be multiplied together.

Area (sq ft) = length × width
Volume (cu ft) = area × (depth in inches ÷ 12)
Cubic yards = cubic feet ÷ 27
Tons = cubic feet × density (lb/cu ft) ÷ 2,000

Take a drive 40 feet long and 12 feet wide. That is 480 square feet. At four inches, the depth in feet is 4 ÷ 12, or 0.333, so the volume is 480 × 0.333 = 160 cubic feet. Dividing by 27 gives 5.93 cubic yards. At a density around 100 pounds per cubic foot, 160 × 100 = 16,000 pounds, which is eight US tons.

Every part of that is arithmetic you can check. The judgement is in the four inches, not in the multiplication.

Most drives are one of a handful of sizes, so the arithmetic above only has to be done once. Every row here is four inches deep, and the tonnage assumes 100 pounds per cubic foot.

Halve the depth and every figure halves with it. The same table works for a landscaping bed, a shed base or a parking pad — the calculator does not care what the rectangle is for.

One Cubic Yard Covers Less Than People Expect

A cubic yard sounds substantial, and at a shallow depth it is. Spread thicker, it disappears quickly — and because the relationship is inverse, doubling the depth halves the coverage exactly.

Each figure is 27 divided by the depth in feet, nothing more. It is worth keeping the four-inch row in mind: a single cubic yard covers about the footprint of a small bedroom at driveway depth, which is why drives are ordered by the load rather than the bag.

Suppliers sell by weight, so the same question is worth answering in tons. At 100 pounds per cubic foot a ton is 20 cubic feet, and coverage follows the same inverse rule.

A ton covering sixty square feet at driveway depth is the figure worth remembering, because it turns a quote in tons back into something you can picture.

Depth Is Where the Money Goes

Area is fixed by your plot. Depth is the one input you choose, and it scales the cost in a straight line — going from three inches to four is a third more stone, a third more weight and a third more to pay, on exactly the same footprint.

That makes it worth being deliberate rather than generous. Too thin and the stones sit as loose individuals: they scatter under tyres, migrate to the edges and show the surface beneath within a season. Too deep and the surface stays soft to walk and drive on, because there is no longer anything solid close under the stone. The useful rule is that a layer needs to be a few times the size of the stone in it for the pieces to interlock at all, which is why a nominal two-inch stone cannot make a sensible two-inch layer.

Depths get quoted in fractions on site — two and a half inches, three and three quarters — while this calculator wants a decimal. The mixed number calculator converts one into the other, which is quicker than reasoning about eighths at the tape.

Yards, Tons and the Number That Connects Them

A calculator gives volume because volume is what fills a space. A supplier quotes weight because a lorry crosses a weighbridge. Neither is being awkward — they are simply measuring different things, and density is the bridge between them.

The conversion falls out of the definitions. A cubic yard is 27 cubic feet. At 100 pounds per cubic foot that is 2,700 pounds, and since a US ton is 2,000 pounds, one cubic yard is 1.35 tons. Lighter material shifts the ratio proportionally, so pea gravel near 96 pounds per cubic foot gives 1.30 tons per yard, and a lightweight decorative stone at half the density gives half the tonnage for the same hole.

This is also why two correct answers can disagree. If your calculation assumes 100 pounds per cubic foot and the quarry works to 105, the tonnage differs by five per cent while the volume you actually need has not moved at all. When they disagree, trust the volume and let the supplier convert it with their own figure.

Pea Gravel, River Rock and Crushed Limestone Do Not Weigh the Same

Volume is set by the hole you are filling. Weight is set by what you put in it, and the spread between landscaping stones is wide enough to change a delivery. These are typical loose dry densities — the figures this calculator starts from, and ones you should overwrite the moment a supplier gives you theirs.

Two things are worth taking from that table. Most stone clusters within a few per cent of each other, so swapping pea gravel for crushed limestone changes the tonnage a little and the volume not at all. Lava rock is the exception that proves the point — at roughly half the density it fills the same space for half the weight, which is exactly why it turns up on roofs and in raised beds.

The figures also move with condition rather than just material. The same stone measured loose, compacted and soaking wet can differ by a quarter or more, which is why published densities disagree with each other and why no single number deserves to be treated as fixed. Use the volume as the firm output and let weight follow from whichever density applies on the day.

Bags or a Bulk Load

The crossover is not a matter of taste, it is division. A cubic yard is 27 cubic feet, so at half a cubic foot per bag it is 54 bags. At around 50 pounds each that is well over a ton to lift twice — once into the car and once out of it — plus 54 empty sacks to deal with.

Bags earn their place for small, precise, awkward jobs: a border, a pot, a patch, somewhere a tipper cannot reach. Past roughly a cubic yard the handling dominates, and a delivered load is usually cheaper per unit as well as very much easier. The meter in the results panel shows where your project sits on that line.

Circles, Triangles and Drives That Are Neither

Only the area step changes with shape. A circular area is π times the radius squared, so a firepit surround ten feet across has a radius of five and an area of π × 25 = 78.5 square feet. A triangle is half the base times the perpendicular height — the height measured square to the base, not along a sloping side, which is the usual slip.

Anything genuinely irregular is best broken into rectangles and added. An L-shaped drive is two. A path that widens at the gate is two. A parking area with a turning spur is two or three. This beats averaging an awkward width, because an average that is a foot out is a foot out along the entire length — on a 40-foot drive that single foot is 40 square feet of stone you either lack or have paid for.

For measurements that arrive in mixed units, the unit conversion calculator will square them up first, and the percentage calculator will handle a settling allowance if you would rather work it out separately. The volume sums underneath all of this — a cuboid's volume, and the cubic feet to cubic yards factor that trips people up most often — are written out in the formula library.

Why the Finished Depth Is Less Than the Depth You Spread

Loose stone does not stay where it lands. Traffic pushes the pieces into each other until they lock, and on anything soft a proportion presses down into the ground and is simply gone from the surface. Both effects reduce the depth you end up with relative to the depth you bought.

How much to add depends entirely on what is underneath — a well-prepared compacted base takes very little, while stone tipped onto soft soil can lose a noticeable fraction before it stops moving. That is why the settling allowance on this calculator starts at zero. You see the plain arithmetic first, then add your own figure knowing exactly what it is doing, rather than inheriting a hidden margin someone else chose.

What This Number Does Not Cover

The cost shown is material only. Delivery is commonly billed separately and varies with distance, load size and access. Excavation, edging to stop the stone migrating, a separating membrane, compaction plant hire and disposal of whatever you dig out are all real costs on a real driveway and none of them appear here.

Treat the output as the figure to hand a supplier when asking for a material quote — accurate for what it measures, and deliberately silent about what it does not.

Most jobs need more than one material, and the quantities are worked out the same way each time: area, depth, then a conversion into whatever the supplier sells. The building and landscaping calculators run that same arithmetic for the rest of them.

Questions About Gravel Quantities