Enter the area to cover and the depth in mm — we work out m³, tonnes and the number of 850 kg bulk bags for gravel, sharp sand or topsoil.
Bulk densities used: gravel 1.6 t/m³, sharp sand 1.6 t/m³, topsoil 1.3 t/m³. Bulk bag size 850 kg is UK/EU standard.
Loose 20 mm gravel weighs ~1.5 t/m³. A 3 × 4 m driveway to 50 mm depth = 0.6 m³ ≈ 0.9 tonnes — one bulk bag.
Bulk bags (~800 kg) are cheaper per kg above 3 bags but loose tipper delivery wins above 5 tonnes if you have access. Bags win on tidy driveways or small jobs.
Pedestrian patio: 100 mm compacted MOT Type 1. Driveway with car: 150 mm. Add 30 mm sharp sand or bedding mortar on top before slabs.
No — pea gravel is round and never locks together, so slabs sink. Use angular crushed aggregate (MOT Type 1 in the UK, 0/31.5 in the EU) that compacts to a rigid layer.
Estimates only. Check the paint tin / adhesive bag for the exact coverage of your product.