How Many Tons of Asphalt for an 18 by 36 Driveway?

Eighteen by thirty-six is an awkward 648 square feet that will not follow a car-count slogan. Plan about 7.8 tons at two inches and about 11.7 tons at three inches. Those are planning estimates. The plant ticket is the real weight.

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Odd dimensions still use the same chain

This awkward rectangle comes out to 648 square feet once 18 is multiplied by 36. There is no special rule because neither side is a round ten. At two inches, 648 times 2 times 145 divided by 24,000 equals 187,920 divided by 24,000, which is 7.83, about 7.8 tons. At three inches, 648 times 3 times 145 divided by 24,000 equals 281,880 divided by 24,000, which is 11.745, about 11.7 tons. One inch on this area is 648 times 145 divided by 24,000, about 3.9 tons, and the two depths are two and three times that slice within rounding. These are planning estimates at 145 pounds per cubic foot of compacted hot mix. The plant ticket is the real weight. Write 648 beside the tons so a later note does not swap in a 16 by 40 just because the tons look similar.

Close to 16 by 40, not the same driveway

A 16 by 40 rectangle is 640 square feet, about 11.6 tons at three inches. This 18 by 36 is 648 square feet, about 11.7 tons. The tonnage is almost the same and the shape is not. Eighteen feet may fit parked cars differently than sixteen, and thirty-six feet of length is four feet shorter than forty. If your tape says 18 and 36, order this area. If it says 16 and 40, order that one. Borrowing either total for the other is a small miss on paper and a wrong sketch in the field. Add a flare on top of whichever rectangle you measured. The flare is not hidden inside the eight square feet that separate 640 and 648.

Check the corners before you multiply

An eighteen-foot width that narrows at a gate is a trapezoid. Average the widths instead of using 18 everywhere. A thirty-six-foot length that includes a turn is two pieces, and the shared corner should be subtracted once if you measured both pieces as full rectangles. Then convert the net area. Hand work around a gate post can thicken the mat beyond 7.8 or 11.7. The gravel base, if you are placing one, is a separate planning weight near 1.4 tons per cubic yard, confirmed by the quarry ticket. Two inches versus three inches remains a site decision, not a code citation from this math. After the job, the tickets summed are what you bought.

A practical sequence

Multiply 18 by 36 to get 648 square feet.
Plan about 7.8 tons at two inches or about 11.7 tons at three inches.
Do not swap this total with a 16 by 40 just because both are near 11.6 tons.
Call it a planning estimate and match the order to the plant ticket.

The mistake to skip

Replacing 18 by 36 with 16 by 40 because the tonnage looks almost the same.

Questions people ask

How many tons is 18 by 36 at three inches?

About 11.7 tons. Eighteen times 36 is 648 square feet, and 648 times 3 times 145 divided by 24,000 equals 11.745. About 7.8 tons is the two-inch planning figure. The plant ticket is the real weight, and a different density would change the result.

Why is this so close to a 16 by 40?

Because 640 and 648 square feet are only 8 square feet apart. At three inches that is a fraction of a ton, about 11.6 versus about 11.7. The shapes still park differently. Measure both sides instead of picking the tonnage you remember.

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