Asphalt calculator

Asphalt is the one material on this site where the unit you buy and the unit you measure have nothing in common. You measure a driveway in square feet. The plant sells by weight. Between them sits a density, and everything about getting the order right is that conversion.

The trade does not do it through cubic feet. It uses a spread rate: pounds per square yard per inch of compacted depth. For hot mix at about 148 pounds a cubic foot, that is 111 — and once you have that number, an area turns into a tonnage in one step.

The familiar rule — “a ton covers eighty square feet” — is the two-inch row of that table, rounded. It is genuinely useful and it is true for exactly one depth. At three inches a ton covers little more than fifty square feet, and quoting the rule at that depth under-orders by a third.

Every depth in any specification, on this page, and in any quote worth having is the compacted depth: what is there after the roller has finished. The paver does not lay that. It lays about a quarter more, and the roller takes it down.

So a two-inch driveway is spread at roughly 2.5 inches. This matters twice. A screed set to two inches leaves a driveway an inch and a half thick when it is rolled — which is thin enough to matter. And a tonnage worked out from the loose thickness over-orders by the same quarter, which on a modest driveway is two tons of asphalt you have paid to have delivered and nowhere to put.

Order the tonnage from the finished depth. The loose thickness is the paving crew’s problem and they already know it.

As many people search for what asphalt driveway repair costs as for what a new driveway costs, and almost every answer is a range that covers everything from a bucket of sealer to a rebuild. The range is useless because they are three different jobs.

What decides between them is not how bad the surface looks. It is whether the base underneath is still carrying load.

Sealcoating is the most oversold operation in residential paving, and it is also genuinely worth doing. Both things are true, and the difference is in what you expect from it.

What it does: it puts a sacrificial coating over the bitumen, which is what ultraviolet light and spilled fuel attack. That slows the oxidation that turns a surface grey and rough. And it makes the driveway black again, which is most of why people buy it.

What it does not do: carry any load, fill any crack of consequence, or fix anything at all beneath the surface. A sealed driveway with a failing base is a failing base with a fresh coat of paint.

And it can be actively harmful. Applied every year — which is what a great many driveways get, because the salesman comes round every spring — it builds into a thick, brittle layer with no flexibility, and that layer cracks and peels away in sheets. Every 3 years or so is protection. Every year is damage.

Asphalt is a flexible pavement. It does not span anything — it spreads load into what is underneath, and if what is underneath moves, the asphalt moves with it and cracks.

Under a residential driveway that means six to eight inches of compacted crushed aggregate, laid in lifts and rolled, on a subgrade that has itself been compacted and graded to fall. It is the same base rock that goes under a patio, for the same reason, and the gravel calculator prices it from the same data.

The failure mode is almost always water. Water in the base softens it, and a soft base under a wheel load is what produces alligator cracking. In a cold climate it also freezes, lifts the pavement and drops it again every winter. Which is why the grade matters as much as the depth: a driveway that sheds water lasts, and one that ponds does not, whatever it was built from.

Recycled asphalt millings are old pavement ground up and sold back. At roughly a quarter of the price of hot mix they are a real option for a long rural drive, and they are routinely oversold as “asphalt for a fraction of the cost”, which they are not.

What they are: a granular material with some residual bitumen in it that compacts into a firm, dark surface and darkens further as the sun works on it. Laid four inches deep and properly rolled, on a prepared base, it makes a good drive.

What they are not: a bound pavement. There is no binder being reactivated unless the material is heated, so it never achieves the strength or the smoothness of hot mix, and it will always shed some loose material.

The thing nobody mentions is that millings are ungraded. Their composition depends entirely on the road they came from — a supplier who cannot tell you the source and whether the load has been screened is selling you an unknown, and a load with large chunks in it will not compact flat at any price.

Almost every oddity in how asphalt is bought comes from one fact: it is only workable while it is hot. It leaves the plant above 300 °F and it has to be laid, screeded and compacted before it drops below about 185 °F. After that the roller is just driving over it.

That is why you cannot buy a wheelbarrow of it, cannot keep it overnight, and cannot pave half a driveway on Saturday and the rest on Sunday. It is why plants set a minimum load — typically around 3 tons — and why a small job is priced against a crew and two machines rather than against a quantity of material.

It is also why paving is seasonal. On cold ground a thin lift loses its heat in minutes, and the crew runs out of working time before the compaction is finished. Uncompacted asphalt has voids in it, water gets into the voids, and it ravels apart early. Most contractors stop below about 50 °F ground temperature, and they are right to.

An asphalt quote divides into three: the material, which is tonnage times a price that tracks the oil market; the base and the excavation, which is where the durability is bought; and mobilisation, which buys nothing at all and cannot be avoided.

The material is a smaller share than people expect. On a typical residential driveway the asphalt itself is often under a third of the bill — which is why a contractor who is cheaper is rarely cheaper on material. The saving is in the base depth, the compaction, or the number of lifts, and all three are invisible the day the job is finished.

Only labour is adjusted for where you are. Asphalt price moves with crude oil and with how far the plant is — it cannot travel far before it cools, so haul distance is a genuine constraint rather than a freight line — while the crew rate moves with the local market. The regional price index is what is being applied.

Compacted density, the spread rate and the lift limits come from the asphalt institute’s construction manual; driveway build-ups, the overlay-versus-reconstruct judgement and the sealcoat interval follow the national paving association’s residential guidance. The base is priced from the same aggregate survey the gravel calculator uses, because it is the same stone. Everything is on the sources page, dated.

Three assumptions worth stating. Every depth is compacted, and the loose thickness is shown separately rather than folded in. The tonnage is given as a range across the density band as well as a single figure, because 145 and 150 lb per cubic foot are both ordinary and the difference is real. And the three courses are priced with what each buys in years, because a driveway is paid for over its life and not on the day.

Nothing you type is sent anywhere — the whole calculation runs in your browser.

Compacted depth and alligator cracking are the two worth knowing: one decides what you order, the other decides whether you should be ordering at all.