Which stone for which job?
Crushed stone is sold in grades named after the size of the pieces. Mixes that include fine dust, like 0 to 32 mm, compact into a hard base. Clean grades with no fines, like 8 to 16 mm, drain freely and stay loose.
0 to 32 mm
Packs down hard and flat.
Best for path and drive sub-bases
8 to 16 mm
Clean stone that drains well.
Best for drainage and soakaways
Granite chippings
Angular and colourful. Stays in place.
Best for decorative top layers
Limestone
Pale and affordable. Compacts well.
Best for tracks and bases
Planning the rest of the job? Use the Pea gravel calculator and the Landscape rock calculator too.
How deep should stone be?
How does the calculation work?
Tonnes = area (m²) × depth (m) × density × 1.1
A driveway 10 m by 3 m with a 20 cm sub-base: 30 × 0.2 = 6 m³. At 1.7 t/m³ that is 10.2 tonnes, or about 11.2 tonnes with 10% for compaction.
Crushed stone with fines shrinks by around 10 to 15% under a plate compactor. Add that to your order so the finished base reaches the right height.