How to Calculate Driveway Sealer in Five Simple Steps

Sealer in one line

Sealer is simple: driveway area, divided by the coverage on the label, times the coats, rounded up to whole gallons. A 20 ft by 12 ft driveway is 240 square feet, one gallon covers 250 square feet in one coat, so one coat takes 0.96 gallons and two coats take 1.92 gallons exact, rounded up to 2 gallons. The rest of this guide is about getting those three inputs honest: the driveway area, the label coverage, and the coats.

Step 1: Measure the driveway, length and width

Measure the driveway in feet, length and width, at the ground itself. The worked example is 20 ft long and 12 ft wide, a common two-car driveway, and the two together give the area the sealer must cover. If the driveway is not a rectangle, measure each section separately and add the areas: an L-shaped driveway is several sections, and the sealer follows the total area, not the longest side.

Step 2: Multiply length by width for the area

Multiply length by width for the driveway area, since sealer covers area, not length. The example is 20 times 12, or 240 square feet. Do not skip this step: a driveway measured by its length alone is only 20 feet, and sealer bought for the length leaves most of the drive bare. Width matters as much as length — a foot wider on the same driveway is another strip of sealer all the way down.

Step 3: Divide the area by the coverage

Divide the area by the coverage on the sealer label for one coat. The example area is 240 square feet and one gallon covers 250 square feet, so 240 divided by 250 is 0.96 gallons a coat. A thinner sealer changes this step most: the same driveway at 300 square feet a gallon needs only 0.8 gallons a coat, while a thicker sealer needs more, and the driveway itself never changes.

Step 4: Multiply by coats and round up

Multiply the one-coat figure by the coats, then round up to whole gallons, since sealer is sold by the gallon. Two coats on the example is 0.96 times 2, or 1.92 gallons exact, rounded up to 2 gallons, and the spare fraction is not wasted — it is the sealer the edges and the second pass consume. Round up at the end, not at the start: rounding one coat first and then multiplying double-counts the rounding and over-orders.

Step 5: Buy, prep and check the driveway

Buy the sealer — 2 gallons for the example — and prep the driveway before sealing: sweep it clean, fill the cracks, and let it dry. Then check the driveway before the first coat: every edge masked, the first pass even, the second pass after the first has dried. Then count what gallons do not cover: crack filler, edge prep and primer. For the driveway itself sized out, the driveway calculator counts the rest, so the sealer and the driveway are ordered together.

Sealer in numbers

Suppose the driveway is 20 ft long and 12 ft wide, the sealer covers 250 sq ft a gallon, and the driveway gets 2 coats. Area: 20 × 12 = 240 sq ft. Sealer per coat: 240 ÷ 250 = 0.96 gallons. Sealer exact: 0.96 × 2 = 1.92 gallons. Sealer to buy: 2 gallons, rounded up. Order: 2 gallons, plus crack filler and edge prep bought separately.

Common mistakes

The most common mistake is measuring the length instead of the area, which buys for 20 feet instead of 240 square feet. The second is forgetting the second coat, which buys for one pass and runs short halfway through the second. The third is reading the coverage off a smooth driveway and sealing a rough one, which soaks up more sealer than the label promises. The fourth is rounding up before multiplying by the coats, which double-counts the rounding and over-orders. The fifth is forgetting the crack filler, which seals a driveway and leaves the cracks open.

Worked example, start to finish

A two-car driveway, 20 ft long and 12 ft wide, sealer at 250 sq ft a gallon, 2 coats. Area: 240 sq ft. Sealer per coat: 0.96 gallons. Sealer exact: 1.92 gallons. Sealer to buy: 2 gallons. Result: buy 2 gallons, and buy crack filler and edge prep separately. If the same driveway got 3 coats instead, the need would rise to 3 gallons, but the driveway sealed would be identical in size.

What changes the answer most

The coats change the answer most after the area: moving from 2 coats to 3 lifts the order from 2 to 3 gallons, while the driveway itself never changes size on the ground. The area is second: every foot of driveway at 250 sq ft a gallon is another fraction of a gallon, and a wrong measurement rebuilds the whole order. The coverage is third, and it changes only the division, never the area — moving from 250 to 300 sq ft a gallon still buys 2 gallons, since 1.6 still rounds up to 2. The rounding is fourth, and it changes only the top of the order, never the maths beneath it.

Frequently asked questions