What is pea gravel?
Pea gravel is small, smooth, rounded stone, usually 6 to 10 mm across. It is comfortable to walk on, drains well and comes in soft browns, greys and creams. Because the stones are round they move underfoot, so it suits paths and seating areas more than steep slopes.
How deep should pea gravel be?
Too thin and the base shows through. Too thick and it feels like walking on a beach.
How does the calculation work?
Tonnes = area (m²) × depth (m) × density (t/m³)
A path 10 m long and 1 m wide at 5 cm: 10 × 0.05 = 0.5 m³. At 1.6 t/m³ that is 0.8 tonnes, or about 32 bags of 25 kg.
Gravel is sold by weight but you measure it by volume, which is why density matters. Wet gravel is heavier, so suppliers may quote a little more.
Bags or bulk?
Bags are handy for small patches and topping up. For a whole path or patio, bulk bags are cheaper per tonne and save a lot of lifting. Most bulk bags hold between 700 kg and one tonne, so check with your supplier.