Why gravel is bought by volume and sold by weight
A gravel job is measured as a volume — an area covered to a depth — but suppliers quote and deliver by the ton. Converting between the two is where estimates go wrong, because the conversion depends on a density that genuinely varies. Published figures for the same material span a fifth or more: pea gravel is cited anywhere from 2,400 to 3,200 lb per cubic yard, and wet or compacted material sits higher still.
This calculator therefore shows three weights rather than one. The middle figure uses a midpoint density; the low and high figures bracket the range the material realistically arrives in. If a supplier's quote falls inside that band, your estimate and theirs agree — a single number to two decimal places would only have implied a precision that does not exist.
Using this gravel calculator
Enter the footprint and how deep the gravel will lie. The results update as you type: volume in cubic yards or cubic metres, the weight band, the area covered, and a count of half-cubic-foot bags for small jobs.
Depth is the field worth thinking about. Paths and slab bases want 2–4 inches; a driveway wants 4–6, and often two layers with a coarser base beneath a finer top. The material selector changes the density used for the weight figures — pea gravel is lightest, river rock heaviest, crushed stone between them. Shape and units live in the customize panel, so an L-shaped or circular area can be entered as a border, circle, triangle or trapezoid instead of being approximated as a rectangle.
Extra for compaction defaults to 5% and is already included in every figure. Loose gravel settles once it is driven on or tamped, so the volume that fills the space after compaction is larger than the space itself.
The formula, worked through
Area in square feet times depth in feet gives cubic feet; divide by 27 for cubic yards; then multiply by density for weight.
A 20 ft × 10 ft path at 3 inches deep is 200 sq ft × 0.25 ft = 50 cubic feet, or 1.85 cubic yards. Add 5% for compaction and it is 1.94 cubic yards. In crushed stone at roughly 3,050 lb per cubic yard, that is about 2.96 tons — with 2.6 to 3.3 tons the honest range.
Two traps live in that chain. Depth is given in inches and must be divided by 12 before it multiplies a square-foot area, and tons per cubic yard is not a fixed constant to memorise. The commonly quoted “1.4 tons per yard” is a midpoint for one particular material in one particular condition, not a law.
Bags, bulk, and choosing a depth
The bag count is there for genuinely small jobs. A bag of aggregate holds half a cubic foot, so a single cubic yard is 54 of them — past about a third of a yard, bulk delivery is cheaper per unit and far less work, and most suppliers have a one-yard minimum anyway.
Going deeper than the job needs is the most expensive mistake available here, because cost scales directly with depth: a driveway laid at 6 inches instead of 4 costs 50% more before a stone has been moved. Conversely, too shallow a layer over soft ground will simply disappear into it — which is what landscape fabric under the base is for.
If the gravel is a base for a slab, size the pour itself with the concrete calculator using the same footprint, and the sand calculator handles a bedding layer over the top.
FAQ
How many tons of gravel are in a cubic yard?
There is no single answer, and any calculator that gives you one to three decimal places is overstating what it knows. Density shifts with the stone, its moisture content, and how much it's been compacted:
| Material | Tons per cubic yard |
|---|---|
| Pea gravel | 1.2 – 1.6 |
| Crushed stone | 1.35 – 1.7 |
| River rock | 1.4 – 1.75 |
Wet gravel can run several hundred pounds per yard heavier than dry, because water fills the voids between stones. This calculator shows a midpoint plus the low and high ends of the range — order against the high end if you're paying by the ton and can't easily get a second delivery.
How deep should gravel be?
Depth is set by what will travel across it:
Driveways are usually built in layers rather than one deep pour: a coarse base course, then a finer top course. If you're doing that, run this calculator once per layer with its own depth.
Why buy gravel by the yard instead of in bags?
Cost, past a surprisingly low threshold. A standard bag holds about half a cubic foot, so a cubic yard is 54 bags. Bagged aggregate typically costs several times as much per cubic yard as bulk delivery, and you still have to move 54 bags.
Bags make sense under roughly a third of a yard — small repairs, a planter, setting a few posts. Anything bigger, price a bulk load.
How much extra should I order?
5–15%. Loose gravel settles once it's tamped or driven on, and a bed that measured 4 inches on delivery day will read closer to 3½ after a season. That settlement is on top of the usual spillage and uneven subgrade.
Toward 15% for driveways and anything that will be compacted deliberately; 5% is fine for a decorative bed nobody walks on.
My driveway isn't a rectangle. Can I still use this?
Yes — open the customize panel (the sliders icon at the top right of the calculator) and switch shape. Circle and circle border handle fire pits and tree rings; trapezoid handles a drive that widens toward the road; triangle handles a corner. The diagram redraws with your dimensions labelled so you can check you've measured the right sides.
For an irregular outline, split it into shapes, run each one, and add the volumes.
What is this gravel usually going under?
Most often a concrete slab. Size the pour itself with our Concrete Calculator — same footprint, different depth and material.
For planting beds rather than hardscape, the Mulch Calculator runs the same shape-and-depth math against retail bag sizes.