How to use this calculator
- Choose an area mode. Rectangle for driveways, paths, and beds measured edge to edge; circle for tree rings and round beds measured by diameter; multiple areas for projects that combine shapes — each area gets a name, a shape, and its own depth.
- Enter dimensions and depth. Depth accepts inches or feet (US) and millimetres, centimetres, or metres (metric), per area. The depth your project needs depends on its use — driveways need far more than decorative coverage; confirm with your supplier.
- Set a waste allowance for uneven ground, low spots, and depth variation. 10% is a starting point, not a rule — rough subgrade and irregular shapes justify more.
- Optionally pick a material and enter a bulk density to add a weight estimate. Pea gravel and crushed stone ship with rounded reference estimates; the other materials deliberately ship empty — use a figure from your supplier.
- Estimate one or both purchase options: by volume at your price per cubic yard or cubic metre, and by weight at your price per ton — only when a density is entered. Set purchase increments to round the order to whole yards or tons.
The formulas
Circle: area = π × (diameter ÷ 2)²
Volume = area × depth
Required volume = base volume × (1 + waste %)
Estimated weight = required volume × bulk density
Multiple areas each use their own depth, and their volumes are added before the waste allowance is applied. The only rounding is to the purchase increment you configure — without one, the exact (fractional) quantity is shown, because suppliers can sell fractional yards.
Worked example
A 20 × 10 ft driveway, 4 inches deep, 10% waste, crushed stone at an assumed 100 lb/ft³, ordered by the cubic yard with a 1-yard increment:
| Step | Result |
|---|---|
| Area: 20 × 10 | 200 sq ft |
| Volume: 200 × (4 ÷ 12) | 66.7 cu ft ≈ 2.47 cu yd |
| Required with waste: 2.47 × 1.10 | 2.72 cu yd |
| Order quantity (1-yd increments) | 3 cu yd |
| Estimated weight: 73.3 cu ft × 100 lb/ft³ | 7,333 lb ≈ 3.67 US tons |
| Cost at, say, $60 per yard | 3 × $60 = $180 |
The $60 figure is an example, not a market claim — enter the price your own supplier quotes, or leave both price fields empty and the calculator shows quantities only.
Volume vs weight — and why density matters
Suppliers sell loose gravel two ways: by volume (cubic yards or cubic metres) or by weight (tons or tonnes). The two are not interchangeable without a density assumption, because the same volume of pea gravel and compacted crushed stone do not weigh the same. Bulk density varies with particle grading, moisture, stone type, and compaction — which is why the calculator treats weight as strictly optional, labels it an estimate, and shows exactly which density it used. Preset densities for pea gravel (≈ 95 lb/ft³) and crushed stone (≈ 100 lb/ft³) are rounded planning values from common reference tables; a figure from your own supplier is always better.
Waste allowance — what it actually covers
Loose material fills low spots, spreads unevenly, and settles. How much extra you need depends on surface irregularity, ground preparation, compaction, depth variation, material grading, and the shape of the project. What the estimate does not do is model compaction or settlement silently — if your supplier quotes compacted volumes, compare the base numbers, not the waste-adjusted ones.
Common mistakes
- Measuring the surface but forgetting that soft ground eats depth — the first lift disappears into the subgrade.
- Comparing a per-yard price against a per-ton price without converting through density — pick one basis and compare like with like.
- Adding the volume order and the weight order together — they are two ways to buy the same pile, never two piles.
- Assuming one depth fits every project — a driveway, a path, and a decorative bed have very different needs.
- Forgetting delivery, minimum-load charges, and spreading — the material is only part of the job's cost.
This is a material estimation tool — results are not a geotechnical, drainage-engineering, or structural design recommendation. Drainage layers, base courses under paving, and load-bearing applications need assessment by a qualified professional.
FAQ
How much gravel do I need for a 20 × 10 ft driveway?
The area is 200 sq ft. At 4 inches deep: 200 × 4 ÷ 12 = 66.7 cubic feet, which is about 2.47 cubic yards (one cubic yard is 27 cubic feet). Adding a 10% waste allowance brings it to roughly 2.7 cubic yards — with a 1-yard purchase increment you would order 3 yards. The Gravel Calculator runs this same math for any shape and depth.
Why does buying by weight need a density?
Volume and weight are different quantities — you cannot convert between them without a bulk density assumption. Gravel density genuinely varies: moisture, particle grading, stone type, and compaction all shift it. That is why the calculator leaves weight blank until you provide a density, ideally from your supplier, and clearly labels the result as an estimate.
What waste percentage should I use for gravel?
It depends on surface irregularity, ground preparation, compaction, depth variation, material grading, and the shape of the project — there is no universal number. 10% is a reasonable starting point for prepared, roughly level ground; uneven subgrade, irregular shapes, or hand-spreading often justify more. The field is editable on purpose.
How many cubic feet are in a cubic yard?
27 — a cubic yard is a box 3 × 3 × 3 feet. Suppliers sell loose gravel by the cubic yard in the US and by the cubic metre elsewhere (1 cubic yard ≈ 0.765 m³). Bags and small loads are often quoted in cubic feet, so the calculator shows all three units at once.
Does the estimate include delivery and spreading?
No. The estimate covers the material quantity only. Delivery fees, taxes, minimum-load charges, spreading or installation labor, site preparation, and compaction equipment are all extra — ask your supplier for the delivered, all-in price and compare it against your material estimate.