How to Figure Asphalt Tons When the Driveway Flares

Treat a flare as a trapezoid. Average the two widths, multiply by the flare length, and add that area to the straight drive. A flare 10 feet long, from 12 feet to 20 feet wide, is 160 square feet and about 2.9 tons at three inches.

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Average the two widths

A flare is wider at the street than at the straight drive, so a single width will miss the area. Add the narrow width and the wide width, then divide by 2. In the planning example the flare is 12 feet at the drive and 20 feet at the street. The average is 16 feet. The flare is 10 feet long, and 16 times 10 is 160 square feet. That piece is only the flare. Add it to the straight run, which you measure as its own rectangle. Do not average the street width back into the whole driveway length or you will thicken the tons on the narrow part too. This trapezoid method is plane geometry. It is a planning area, and it still needs a thickness before it becomes tons.

About 2.9 tons for that piece

At three inches, 160 times 3 times 145 divided by 24,000 equals 69,600 divided by 24,000, which is exactly 2.9 tons. At two inches the same 160 square feet is 160 times 2 times 145 divided by 24,000, about 1.9 tons. The straight driveway is additional. A 12 by 40 foot run is 480 square feet, about 8.7 tons at three inches, and the flare's 2.9 brings a combined planning total near 11.6 tons before other waste. This is a planning estimate at 145 pounds per cubic foot. The plant ticket is the real weight. If you pave only part of the flare, remeasure the width you will actually place.

Measure the opening you will pave

The street end is only as wide as the pavement you are actually going to build. Do not assume a flare can run as far down the gutter as a sketch looks nice. Measure that width on the ground. Aprons that meet a sidewalk, a curb cut, or a neighbor's edge stop where those limits are. This page does not decide the legal edge of a right of way. It converts the area you measured. Flares are often placed by hand, so the compacted depth can run thicker than the three inches in the formula. After the pour, include the flare in the measured area when you compare tickets with the plan. Leaving it off the sketch is how short orders happen.

A practical sequence

Average the width at the drive and the width at the street.
Multiply that average by the length of the flare to get square feet.
Add the flare area to the straight run, then convert at one thickness.
Use about 2.9 tons for this 160 square foot example at three inches, as a planning estimate checked by the plant ticket.

The mistake to skip

Ordering the straight rectangle and forgetting the flare that widens at the street.

Questions people ask

How do I find the area of a flare?

Average the two ends. A flare that is 12 feet wide at the drive and 20 feet wide at the street has an average width of 16 feet. Times a 10-foot length, that is 160 square feet. Then multiply by the thickness using 145 pounds per cubic foot. The plant ticket is the real weight.

Does the 2.9 tons include the rest of the driveway?

No. It is only the 160 square foot flare at three inches. Add the straight run as its own rectangle. If that run is 12 by 40, it is about 8.7 tons at three inches, and the pieces together are about 11.6 tons before other waste.

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