Work out how many tonnes or bulk bags of Type 1 (MOT) you need for a patio, path or driveway sub-base.
Area × compacted depth gives the volume of Type 1 once it's been compacted.
We multiply by 2,100 kg/m³, the typical density of compacted Type 1. That already allows for the stone settling under the compactor, so there's no separate compaction factor.
We add your waste allowance for spillage and uneven ground, then round up to whole bulk bags of about 850 kg, or to the next 0.1 t. From about 10 t, a loose tipper load is usually cheaper.
These are estimates for ordering materials, not a structural design. Check site conditions, and anything unusual, with a qualified builder or engineer.
About 4.8 m² at 100mm deep, or 3.2 m² at 150mm, once compacted.
100mm for patios and paths, 150mm for driveways, and 200mm or more for heavy vehicles or soft ground. Compact it in layers no thicker than about 100mm.
Not quite. Type 1 is graded crushed stone to a Highways specification, with fines that lock it together when compacted. 'Hardcore' can mean any broken rubble, which doesn't compact as well.
Not if, like this calculator, you use the compacted density (about 2.1 t/m³). The waste allowance then covers spillage and uneven digging. Adding a compaction factor as well would double count.