How to use the gravel calculator
- Choose metric or imperial units.
- Pick the type of gravel. Not sure? Choose “Not sure / other gravel” — you'll get a wider range.
- Pick the shape of the area and enter its measurements. For an L-shaped drive, split it into two rectangles and add the results.
- Enter the finished depth you want once it's laid.
- Keep the compaction and waste allowances unless you have a reason to change them. Tick Delivered wet if the stone is washed or it has been raining.
- Optional: type your supplier's density and price for a tailored weight and cost.
The formula
volume = area × depth × (1 + compaction %) × (1 + waste %)
weight = volume × density (low to high for your stone)
bulk bags = top weight ÷ 850 kg (rounded up)
For a circle, the area is π × (diameter ÷ 2)². To convert, 1 cubic yard is 27 cubic feet (0.7646 m³), and 1 US ton is 2,000 lb (0.9072 tonnes). All of this is done for you above.
Worked examples
Metric (UK drive): a drive 10 m long and 3 m wide, 75 mm of crushed stone, with 10% for compaction and 5% for waste:
10 × 3 × 0.075 = 2.25 m³ → × 1.10 × 1.05 = 2.6 m³ → 4.2–4.6 tonnes. Ordering by weight, get 4.6 tonnes, or 6 bulk bags of 850 kg.
Imperial (US driveway): 20 ft by 10 ft, 4 in of crushed stone, same allowances:
20 × 10 × (4 ÷ 12) = 66.7 ft³ = 2.47 yd³ → 2.85 yd³ → 3.9–4.3 US tons. Ordering by weight, get 4.3 tons.
Why gravel weight varies — and why we show a range
The same volume of gravel can weigh quite different amounts. Small rounded stones and angular crushed stone pack differently; fine road base fills the gaps and is heavier; and water adds weight but not volume. Published figures don't agree on one number, so instead of pretending to be exact we show the typical range for the stone you picked:
| Gravel | t/m³ | US tons/yd³ |
|---|---|---|
| Crushed stone (e.g. #57, 20 mm) | 1.6–1.78 | 1.35–1.5 |
| Pea gravel / shingle | 1.54–1.68 | 1.3–1.42 |
| Road base / MOT Type 1 | 1.6–2 | 1.35–1.69 |
| Not sure / other gravel | 1.4–1.8 | 1.18–1.52 |
Figures are for loose, dry-to-damp stone. Ticking Delivered wet adds about 6%. If your supplier gives a weight per cubic metre or cubic yard for the exact stone you're buying, type it in — it will always beat a general average. At the top of the crushed-stone range, one tonne covers about 11.2 m² at 5 cm deep.
Tips before you order
- Check how it's sold. Ask whether the price is per tonne, per US ton, per cubic yard or per bulk bag, and what one bulk bag weighs.
- Buying by weight? Order the top of the range. Running short means a second delivery charge.
- Think about access. Loose loads are tipped where the lorry can reach. Bulk bags can be easier for back gardens.
- Base layers. Driveways often have a compacted sub-base under the decorative top layer. Calculate each layer separately with its own type and depth.
Common mistakes to avoid
- Mixing up tonnes and US tons. A US ton is 2,000 lb (0.907 tonnes) — about 10% less than a metric tonne. Check which one your supplier means.
- Using one weight for every stone. Pea gravel, crushed stone and road base weigh different amounts per cubic yard. Pick the right type, or use your supplier's figure.
- Forgetting the sub-base. If your drive has a compacted base layer under the top gravel, calculate it separately — choose “Road base / MOT Type 1”.
- Ignoring compaction. Rolled gravel ends up thinner than it was delivered. Keep the compaction allowance for drives and bases.
Measuring an awkward shape? See how to measure an irregular area.
Frequently asked questions
How many tons is a cubic yard of gravel?
It depends on the stone. Crushed stone is usually about 1.35–1.5 US tons per cubic yard, pea gravel about 1.3–1.42, and road base (sub-base) can be heavier. Wet gravel weighs more again. That's why the calculator shows a range and lets you type your supplier's own figure.
How many bulk bags of gravel do I need?
UK bulk bags usually hold about 850 kg, and suppliers say one covers roughly 8–12 m² at 50 mm deep. The calculator works out the weight you need and divides by 850 kg, rounding up. For a 10 × 3 m drive at 75 mm deep, that's about 6 bags of crushed stone. If your supplier's bags are 1 tonne, you'll need fewer.
Why does wet gravel matter?
Water adds weight, not volume. If you buy by the tonne and the stone is wet (washed or rained on), each tonne holds less stone. One UK supplier sells the same bulk bag as about 800 kg, “up to 850 kg depending on moisture” — about 6% heavier. Tick “Wet” and the calculator raises the weight to match.
How much extra gravel should I order for compaction?
Gravel that is rolled or compacted (driveways, sub-base) settles, so you need more loose gravel than the finished depth suggests. Published advice ranges from about 5–10% to 10–20%. We use 10% for compaction plus 5% for waste and uneven ground. For loose decorative gravel that you won’t compact, set compaction to 0.
Is gravel sold by weight or by volume?
Both. Many suppliers sell loose gravel by the tonne or ton, others by the cubic metre or cubic yard, and garden centres sell bags and bulk bags. If you buy by volume, order the volume shown. If you buy by weight, order the top of the weight range so you don’t run short.
Sources
- Vertigraph — How to calculate gravel tonnage (crushed stone, pea gravel, road base)
- InvoiceOwl — Gravel calculator (#57 stone density)
- Designing Buildings Wiki — Converting between weight and volume
- Calcforlife — MOT Type 1 calculator UK (loose density)
- MP Moran — Type 1 bulk bag (about 0.5 m³, 800–850 kg)
- Turnbull — 20 mm gravel bulk bag (weight varies with moisture; 8–10 m² at 50 mm)
- Hellogravel — How much gravel for a driveway (compaction allowance)
Last updated 11 November 2026. Found a mistake? Tell us.