Honest material calculator

How much asphalt you actually need

Asphalt is ordered by the ton, laid at compacted depth, and has to go down the day it arrives. Get any of those three wrong and you've bought a truckload of a material that cannot wait.

For driveways, paths and patching. Enter the area and the finished depth — the tonnage comes out compacted, which is what the plant quotes on.

Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.

Related: Gravel calculator · Concrete calculator · Sod calculator

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How the sum works

Area × finished depth, converted at about 2,400 kg/m³. The depth you enter is the compacted depth, which is what the plant quotes on — hot mix compacts roughly 20–25%, so the loose layer you spread is deeper than the finish you want. A 20 m² driveway at 50 mm finished works out at around 2.5 tonnes.

Three things that all have to be right on the day

Asphalt is ordered by the ton, laid at compacted depth, and has to go down the day it arrives. Book the roller with the mix — compaction has to happen while the material is still hot, and a plate compactor is not enough for anything bigger than a patch. Order slightly long rather than short: a cold joint where a second load meets a cooled first one is a permanent line and a future crack. Unlike gravel, you cannot come back next week.

The base matters more than the asphalt

A surface course over a soft or unconsolidated base will fail regardless of how well it is laid. If the sub-base is not right, fix that before ordering any mix. Falls come before depth, too: water sitting on asphalt is what breaks it up over winter, and a minimum fall of about 1 in 60 away from the building is the usual target.

Questions people actually ask

How many tonnes of asphalt do I need?

Multiply the area by the finished compacted depth and by about 2.4 to get tonnes. A 20 m2 driveway at 50 mm compacted is roughly 2.5 tonnes. Depth here is compacted depth, which is what the plant quotes on.

How much does asphalt compact?

Roughly 20–25%, so the loose layer you spread has to be deeper than the finished depth you want. The tonnage this calculator gives already assumes a compacted result.

Can I lay asphalt with a plate compactor?

Only for a patch. Anything larger needs a roller, booked to arrive with the mix, because compaction has to happen while the material is still hot.

Should I order extra asphalt?

Yes, slightly long rather than short. A cold joint where a second load meets a cooled first one is a permanent line and a future crack — and unlike gravel, you cannot top it up next week.