Tarmac Driveway Calculator — Tonnage & Sub-base

A domestic driveway typically needs 50mm of base course (20mm dense bitumen macadam) plus 25mm of wearing course (6mm close-graded macadam), totalling 75mm of tarmac. For commercial or heavy vehicle use, increase the base course to 60-80mm. Both layers are laid separately and compacted with a roller.

Tarmac (asphalt) has a compacted density of approximately 2.3 tonnes per cubic metre. At standard driveway thickness (50mm base + 25mm wearing = 75mm total), you need about 0.17 tonnes (170 kg) per square metre. A typical 50 m² driveway requires around 8.6 tonnes of tarmac.

Tarmac driveways need a compacted Type 1 sub-base (crushed limestone or granite to SHW Clause 803) at least 150mm deep for domestic use. For commercial or heavy-vehicle duty, increase this to around 300mm (trade practice cites 225–300mm, with a structural engineer consulted for HGV loading or poor ground) — this is the figure the calculator uses when you select “Commercial / Heavy Vehicle”. The sub-base must be compacted in layers (maximum 225mm lifts) using a vibrating plate or roller. Type 1 aggregate has a compacted density of approximately 2.1 tonnes per m³.

If your front garden tarmac driveway drains to a permeable area (lawn, border or soakaway), no planning permission is needed under permitted development rules. If the entire surface is impermeable and drains to the road, you'll need planning permission. This applies to areas over 5 m² in England.

Supply-only hot-mix tarmac is roughly £45-80 per tonne in 2026, depending on grade and location. Small loads cost more per tonne because delivery typically adds £100-150 — the calculator’s £85/tonne default reflects a small-load delivered price, so lower it if you can buy in bulk. A typical 50 m² driveway needs around 8-9 tonnes. Installation labour, plant hire (roller) and a skip for excavated soil are additional costs. Always confirm against a current supplier quote.