Gravel Calculator — Tonnes & Cost

Gravel quantity is calculated by multiplying area × depth to get volume, then converting to tonnes using the bulk density. Most decorative gravel has a bulk density of 1.5–1.8 t/m³. A typical driveway uses a 40–50 mm depth of gravel over a compacted sub-base, while paths and borders need 25–40 mm. Take a driveway of 8 m × 3 m: the area is 24 m², at 50 mm deep the volume is 1.2 m³, and at a density of 1.7 that weighs 2.04 tonnes. Divided by 0.85 tonnes per bulk bag that is about 2.4 bags, so you would order 3 bulk bags.

This calculator shows results in cubic metres, tonnes and bulk bags (a standard bulk bag contains approximately 0.5 m³ or 0.8–0.9 tonnes). Enter the area dimensions and desired depth and it returns volume, weight in tonnes, number of bulk bags and an estimated cost. Delivered gravel in the UK typically costs £50–£80 per tonne for standard aggregates, or £80–£150 per tonne for premium decorative gravel, so the 8 m × 3 m drive above comes in at roughly £150–£240 delivered. For quantities of 5 tonnes or more, a loose tipper-truck delivery is much cheaper per tonne than bagged gravel, provided you have the space and access for the lorry.

Prices per bulk bag vary a lot by type. Basic 10mm pea gravel for paths and drainage costs £45-£75 a bulk bag, 20mm Cotswold buff for driveways and decorative work £60-£100, limestone chippings £55-£90, granite chippings £70-£110 and slate chippings £80-£140, with Welsh slate at the premium end. Resin-bound gravel, mixed with resin and laid by a contractor, is priced by area instead at £80-£150/m² and gives the premium driveway finish. Check the origin before buying, because Cotswold gravel from Welsh quarries is darker than genuine Cotswold limestone. A quarry within 20 miles is usually significantly cheaper, since haulage is a large share of the price.

Driveway gravel cannot simply be tipped onto soil, because it sinks, weeds break through and ruts form. A proper build-up from the bottom starts with excavating 250-300mm of soil, then a weed membrane (geofabric), then 150mm of compacted Type 1 MOT sub-base at £40-£60/tonne, then an optional gravel grid such as Nidagravel or X-Grid at £15-£30/m², and finally the decorative gravel topping. The geo-textile membrane prevents weed growth and stops gravel mixing with the sub-base, while the honeycomb grid panels stabilise the surface for vehicles and stop gravel migrating onto the lawn. Without a grid, expect to top up annually. Edging in timber, stone or plastic at £8-£20 per linear metre keeps the gravel where it belongs.

Planning rules matter for front gardens. Since 2008 in England, a new driveway over 5 m² in a front garden needs either a permeable surface or planning permission. The rules were introduced to manage surface water run-off and flooding. Loose gravel that is not bound qualifies as permeable and so counts as permitted development, as does resin-bound porous gravel and block paving with permeable joints and sub-base. Bonded resin, which is impermeable, requires planning permission. Most gravel driveways do meet the permitted development test, but it is worth confirming with your council before laying.

Maintenance is light but not zero. Rake the surface once a year to redistribute the coverage, and top up every 1-3 years if there is no grid, which usually means about half a bulk bag for an average drive. The membrane stops weeds coming up from the ground, but airborne seeds will still sprout and need pulling by hand or treating with glyphosate, which is banned in many cases, so check first. Gravel that scatters onto the road is your responsibility to keep within the boundary, so shovel it back. The heaviest cars will rut a drive without a grid. Snow is awkward to shovel off gravel, and salt corrodes some gravel types.