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.
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 are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing. These quantities are a guide to help you order. Always round up and check with your supplier before buying.