What is river rock?
River rock is stone that water has worn smooth and round. It comes in mixed natural colours, from small pebbles to fist sized cobbles. People use it for dry creek beds, around downpipes, in borders and as a tidy strip along a house wall.
Planning the rest of the job? Use the Pea gravel calculator and the Landscape rock calculator too.
How deep should river rock be?
A good rule is a layer about twice as deep as the stones are wide. That way the stones rest on each other and no soil shows between them.
How does the calculation work?
Tonnes = area (m²) × depth (m) × density (t/m³)
A dry creek bed 6 m long and 1 m wide at 10 cm: 6 × 0.1 = 0.6 m³. At 1.6 t/m³ that is about 0.96 tonnes.
How do I choose a size?
Small pebbles
Easy to rake and walk on. Fills gaps between bigger stones.
Best for borders and paths
Medium stones
The all rounder. Stays put and still looks natural.
Best for drainage strips
Large cobbles
Heavy and stable. Placed by hand rather than spread.
Best for creek beds and edges
Mixed sizes
Looks the most like a real stream bed.
Best for dry creek beds