Aggregate Calculator guide
Aggregate Calculator: How Much Gravel, Sand or Sub-base Do I Need?
Use our aggregate calculator to work out the tonnes and bulk bags of gravel, MOT Type 1 sub-base, sand or topsoil you need for a driveway, path or garden.
By the AllCalculator editorial teamUpdated 15 October 20262 min read
Aggregates are sold by weight, but you measure your garden in metres. Our Aggregate Calculator bridges the gap, turning your measurements into tonnes and bulk bags of gravel, sub-base, sand or topsoil.
How to work out how much you need
- Volume: length × width × depth, in metres. 50mm deep is 0.05m.
- Weight: multiply the volume by the material's density in tonnes per m³.
- Extra: add around 10% for compaction, uneven ground and spillage.
Typical densities
| Material | Tonnes per m³ (approx.) |
|---|---|
| Gravel or decorative stone | 1.6 |
| MOT Type 1 sub-base | 2.1 |
| Ballast (all-in) | 1.8 |
| Sharp sand | 1.6 |
| Building (soft) sand | 1.5 |
| Topsoil | 1.4 |
Densities vary with stone size and moisture, so your supplier's figures may be slightly different.
How deep should it be?
- Decorative gravel: about 50mm.
- Gravel driveway: 50mm of gravel on top of 100mm to 150mm of compacted Type 1.
- Patio or path sub-base: 75mm to 100mm of Type 1.
- New lawn: 100mm to 150mm of topsoil.
How to use the calculator (Aggregate Calculator)
- Choose the material.
- Enter the length, width and depth.
- Check the bulk bag size. Most hold 0.8 to 1 tonne.
A worked example
With the calculator's default settings, a 5m × 3m area of decorative gravel 50mm deep:
- Volume: 5 × 3 × 0.05 = 0.75m³
- Weight: 0.75 × 1.6 = 1.2 tonnes, or about 1.32 tonnes with 10% extra
- Bulk bags at 0.85 tonnes: 2 bags
Ordering tips
- Bulk bags are cheaper per tonne than small bags and are delivered by crane lorry, so check there's access.
- Loose loads by tipper truck are cheapest for big jobs.
- Check the rules for front gardens. Paving more than 5m² of a front garden with a non-permeable surface needs planning permission, but gravel is permeable.
Laying concrete as well? Our Concrete Calculator works out the volume. For costs, see our Driveway Cost Calculator and Square Meter Calculator.
Frequently asked questions
How much does a bulk bag of gravel cover?
At 50mm deep, a 0.85-tonne bulk bag covers roughly 10m² to 11m².
How many tonnes of Type 1 do I need for a driveway?
Multiply the area by the depth, then by about 2.1. A 30m² driveway with 150mm of sub-base needs about 30 × 0.15 × 2.1 = 9.5 tonnes, plus some extra for compaction.
Is a cubic metre of gravel a tonne?
No. A cubic metre of gravel weighs about 1.6 tonnes.
Measure carefully, add a little extra and you'll avoid a second delivery. Use the Aggregate Calculator before you order.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.