A worked example: a 12m by 4m gravel driveway
A 12m long, 4m wide driveway with a 15cm gravel base works out to 7.2 m³ of gravel (12 × 4 × 0.15). At a typical crushed-stone density of 1650 kg/m³, that's 11,880 kg, or 11.88 tonnes, of material — enough for most suppliers to quote as a single truckload rather than several smaller deliveries.
The formula: length times width times depth, converted to weight
The volume of gravel needed is simply length × width × depth, with depth converted from centimeters to meters (dividing by 100) so all three dimensions share the same unit before multiplying. For the driveway above that's 12m × 4m × (15cm ÷ 100) = 7.2 m³. Weight then follows directly: volume × density, so 7.2 m³ × 1650 kg/m³ = 11,880 kg. Density is a supplier-specific figure — 1600-1700 kg/m³ is typical for crushed stone gravel, so always confirm the exact figure with whoever is delivering the material rather than assuming a single universal number.
A second worked example: a narrow garden path
A garden path is a much smaller job. An 8m long, 1.2m wide path with a 7cm gravel depth (a typical depth for a decorative or walking path, shallower than a load-bearing driveway base) needs only 0.672 m³ of gravel (8 × 1.2 × 0.07). At a density of 1600 kg/m³ — at the lighter end of the typical range — that's 1,075.2 kg, or roughly 1.075 tonnes, small enough that many suppliers will deliver it in bags rather than by the truckload.
Why the compaction margin matters
Gravel compacts once it's laid and rolled or tamped down, so ordering exactly the calculated volume tends to leave a job short. Applying a 10% margin to the driveway example above — a common wastage allowance used across bulk construction materials on this site — raises the order from 7.2 m³ to 7.92 m³, a difference worth building into the order up front rather than discovering mid-job when the last few square meters come up short of material.