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Gravel calculator
Put your driveway size, depth and waste in: a 20 ft by 12 ft driveway, 4 in deep, needs 80 cu ft of gravel — 3.26 cubic yards with 10% waste, or 4.56 tons.
★ CONSTRUCTION · DRIVEWAY · GRAVEL
Gravel Calculator: 3.26 Yards for a 20×12 ft Driveway
On the defaults — a 20 ft by 12 ft driveway, 4 in deep, 10% waste — you need 3.26 cubic yards of gravel, or 4.56 tons. This is the gravel tool: measure the driveway once, allow for the settling, and order the delivery once — gravel does not wait for a second lorry.
What does gravel needed 3.26 cubic yards mean?
It means a lorry load of 3.26 cubic yards — about 4.56 tons at the usual 1.4 tons per cubic yard — covers a 20 ft by 12 ft driveway to a depth of 4 in, once spreading waste is allowed for. The bare volume is 80 cubic feet: 20 times 12 times a third of a foot of depth. The 10% waste allowance adds 8 cubic feet for the gravel that settles into the sub-base and the corners that never spread evenly, taking the order to 88 cubic feet. Divide by 27 — the cubic feet in a cubic yard — and the order is 3.26 yards. Suppliers sell by the yard or by the ton, so the page gives both: 3.26 yards, 4.56 tons.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Volume | length × width × depth ÷ 12 | 80 cu ft — 20 × 12 × 4 ÷ 12. |
| With waste | volume × (1 + waste ÷ 100) | 88 cu ft — 80 × 1.10. |
| Cubic yards | with waste ÷ 27 | 3.26 yards — 88 ÷ 27. |
| Tons | cubic yards × 1.4 | 4.56 tons — 3.26 × 1.4. |
Three things to check before you trust the number
First, check the depth with a tape, not by eye: most driveways are shallower at the edges than in the middle, and a driveway that averages 3 in instead of 4 in needs a quarter less gravel — but a driveway that is really 5 in deep needs a quarter more. Second, check how your supplier sells: a yard of pea gravel weighs less than a yard of crushed stone, so if the supplier quotes by the ton, confirm the tons-per-yard rate for your stone before ordering. Third, remember the order is gravel only — it does not include the sub-base, the edging, or the weed fabric underneath, which are separate lines on the same job.
Worked example
20 ft long, 12 ft wide, 4 in deep, 10% waste, 1.4 tons per cubic yard. Volume: 20 × 12 × 4 ÷ 12 = 80 cu ft. With waste: 80 × 1.10 = 88 cu ft. Cubic yards: 88 ÷ 27 = 3.26. Tons: 3.26 × 1.4 = 4.56. In practice that means ordering 3.26 yards — and since a supplier delivers in whole or half yards, rounding the order to 3.5 yards, which leaves a small pile for topping up the thin spots after the first rain. If the same driveway were 6 in deep instead, the volume would be 120 cu ft and the order 4.89 yards, or 6.84 tons, so depth alone would add more than half as much gravel again.
Every branch, checked
With a 30 ft long driveway instead of 20 ft, the volume with waste rises to 132 cu ft and the order to 4.89 cubic yards, or 6.84 tons. With a 16 ft wide driveway, the volume with waste rises to 117.33 cu ft and the order to 4.35 cubic yards, or 6.08 tons. With a 6 in depth, the volume with waste also rises to 132 cu ft and the order to 4.89 cubic yards, or 6.84 tons — length and depth move the volume in the same proportion. With 0% waste, the volume falls to 80 cu ft and the order to 2.96 cubic yards, or 4.15 tons. Every branch moves the volume, and the yards and tons follow it.
The reverses, worked backwards
The length behind 3.26 cubic yards is 20 ft: at 16 ft the need is 2.61 cubic yards (70.4 cu ft with waste, 3.65 tons); at 24 ft it is 3.91 cubic yards (105.6 cu ft with waste, 5.48 tons). The width behind 3.26 cubic yards is 12 ft: at 8 ft the need is 2.17 cubic yards (58.67 cu ft with waste, 3.04 tons); at 16 ft it is 4.35 cubic yards (117.33 cu ft with waste, 6.08 tons). The depth behind 3.26 cubic yards is 4 in: at 2 in the need is 1.63 cubic yards (44 cu ft with waste, 2.28 tons); at 6 in it is 4.89 cubic yards (132 cu ft with waste, 6.84 tons). Each reverse moves one input and holds the rest, so the step is exactly one dimension or one depth change.
What the defaults assume
The defaults assume a 20 ft by 12 ft rectangular driveway, a flat 4 in gravel layer, 10% spreading and settling waste, and 1.4 tons per cubic yard. They do not assume a sub-base layer, a flare at the street, a slope that washes gravel downhill, or a different stone density — a flared entrance should be measured as a second rectangle and added, and a light stone needs its own tons-per-yard rate.
Who uses this
- A homeowner resurfacing a driveway: the 3.26-yard, 4.56-ton order settles the supplier call before the first barrow is filled.
- A DIY builder topping up a gravel path: the same maths on the path’s size gives the barrow count, not a lorry load.
- A contractor quoting a driveway job: volume, waste, yards, tons — the quote follows the same four steps, and the waste line shows the client why.
- A landlord refreshing a rental’s parking area: the driveway size off the plot plan, times depth, gives the gravel line on the refresh budget.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is the depth and the tons-per-yard rate. Real driveways are rarely flat: depth varies across the surface, a soft sub-base swallows the first load, and a yard of light pea gravel weighs less than a yard of crushed stone. Treat 3.26 yards as the planning order for a flat 4 in layer at 1.4 tons a yard, and confirm the stone’s density with the supplier before the delivery day — gravel arrives by the lorry, so the order must be right the first time.
Cite this calculator
Bright Side Kit, “Gravel Calculator: 3.26 Yards for a 20×12 ft Driveway”, https://brightoolbox.com/gravel-calculator/, accessed 2 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (20 ft × 12 ft driveway, 4 in deep, 10% waste, 1.4 tons per cubic yard) so the 3.26-yard result can be checked.
Frequently asked questions
How many cubic yards of gravel do I need for a 20×12 driveway?
3.26 cubic yards with 10% waste, or 4.56 tons. The bare volume is 80 cu ft, waste takes it to 88 cu ft, and 88 ÷ 27 = 3.26 yards.
How many tons is 3.26 cubic yards of gravel?
About 4.56 tons at 1.4 tons per cubic yard, the usual rate for crushed stone. A lighter stone weighs less per yard, so confirm the rate for your stone with the supplier.
How deep should gravel be on a driveway?
About 4 in for a normal driveway, which is the depth this calculator uses. A path can manage 2 in; a driveway that carries heavy vehicles wants 6 in, which takes this driveway to 4.89 yards.
Should I add waste to a gravel order?
Yes — 10% is the usual allowance for spreading, settling and uneven ground. Without it, the last corner comes up thin, and a second small delivery costs more than the spare gravel would have.
Do suppliers sell gravel by the yard or by the ton?
Either, depending on the supplier — which is why this calculator gives both. Order 3.26 yards, or 4.56 tons, and round the delivery up to the supplier’s nearest half yard.
How do I price the gravel once I know the yards?
Multiply cubic yards by the per-yard price and add delivery. The concrete calculator prices a solid slab for the same driveway, if gravel and concrete are being compared.