Tarmac calculator
Work out how much tarmac you need for a driveway or path. Enter the length, width and depth and this calculator gives you the weight in tonnes, the volume and the coverage. Tarmac is laid hot by a contractor, so use this to plan and to sense-check a quote.
Tarmac calculator
Enter your measurements in metres. Everything updates as you type, and nothing is sent anywhere.
Based on a laid and compacted asphalt density of about 2.36 tonnes per cubic metre, with 5% added for waste. A typical driveway surface course is 40mm to 50mm over a binder course and a compacted sub-base; a one-off wearing course on a sound base can be thinner. Tarmac is supplied and laid hot by a contractor, not bought by the bag.
How the tonnage is calculated
The formula is length × width × (depth in mm ÷ 1,000) × 2.36 × 1.05. Depth is the finished compacted layer thickness. The 2.36 tonnes per m³ is this tool’s assumed density, and 1.05 adds 5% for waste; check the actual asphalt mix with your supplier.
For 10 m by 5 m at 50 mm, the volume is 50 × 0.05 = 2.5 m³. The base weight is 5.9 tonnes; with 5% waste it is 6.195 tonnes, displayed as about 6.2 tonnes. A surface course and a binder course need separate calculations using their own specified thicknesses and mix densities.
This is a material-quantity estimate, not a driveway construction design or an installed price. It does not calculate excavation, sub-base, drainage, delivery or labour. Use the driveway cost guide for a project budget and ask the contractor to specify the build-up.
Common questions
How much tarmac do I need?
Multiply the area by the depth for the volume in cubic metres, then by about 2.36 for the weight in tonnes. At 50mm deep, one tonne of tarmac covers roughly 8.5 square metres. The calculator adds 5% for waste and gives you the tonnage to plan around.
How thick should a tarmac driveway be?
Usually a 40mm to 50mm surface course over a 60mm or so binder course and a compacted MOT Type 1 sub-base, so 100mm or more of construction in total. The sub-base does most of the load-bearing work, so do not skimp on it to save on tarmac.
Can I lay tarmac myself?
Not really for a driveway. Hot-rolled asphalt arrives at temperature and has to be spread and compacted quickly with a roller before it cools, which is a contractor job. Cold-lay bagged tarmac exists for small pothole and patch repairs, but it is not a substitute for a properly laid drive.
These quantities are a guide to help you order. Always round up and check with your supplier before buying.