Driveway Sealer Calculator: 2 Gallons for a 20x12 Drive

What does driveway sealer needed 2 gallons mean?

It means two gallons seal a 20 ft by 12 ft driveway with 2 coats. The driveway itself is 240 square feet, since 20 times 12 is 240; one gallon covers 250 square feet in one coat, so a single coat takes 0.96 gallons, and two coats take 1.92 gallons exact, rounded up to 2 whole gallons because sealer is sold by the gallon, not by the fraction. The spare fraction is not spare sealer exactly — it is the sealer the edges, the cracks and the second pass consume, so a driveway sealed to the exact gallon runs short before the last coat.

Output · formula · meaning

Three things to check before you trust the number

First, check the coverage on the sealer label you are actually buying: 250 sq ft a gallon is the common figure, but a thicker sealer covers less per gallon and raises this driveway past 2 gallons, while the driveway area never changes. Second, remember the count follows the area, not the length: a 20 ft by 12 ft driveway is 240 sq ft, and a driveway measured by its length alone under-orders badly. Third, judge the coats honestly: one coat seals a driveway in good shape, but a worn driveway wants 2, since the first coat soaks into the cracks. Edges, cracks and the apron are sealed from the same gallons — see the driveway calculator for the driveway itself sized out.

Worked example

20 ft long, 12 ft wide, 2 coats, 250 sq ft a gallon. 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. In practice that means buying 2 gallons, and expecting the last fraction to go on edges and the second pass. If the same driveway got 3 coats instead, the need would rise to 3 gallons, but the driveway sealed would be identical in size.

Every branch, checked

With a 24 ft long driveway instead of 20 ft, the area rises to 288 sq ft and the need to 3 gallons. With 3 coats, the per-coat need stays 0.96 gallons but the total rises to 2.88 gallons exact and the buy to 3 gallons. With 1 coat, the total falls to 0.96 gallons exact and the buy to 1 gallon. With 300 sq ft a gallon, the per-coat need falls to 0.8 gallons and the total to 1.6 gallons exact, but the buy stays 2 gallons, since 1.6 still rounds up to 2. Driveway size, coats and coverage each move the order on their own, so a wrong coverage figure is as costly as a wrong measurement.

The reverses, worked backwards

The length behind 2 gallons is 20 ft: at 10 ft the need is 1 gallon (10 ft × 12 ft driveway, 120 sq ft, 0.48 gallons a coat, 0.96 gallons exact, 2 coats, 250 sq ft per gallon); at 24 ft it is 3 gallons (24 ft × 12 ft driveway, 288 sq ft, 1.15 gallons a coat, 2.3 gallons exact, 2 coats, 250 sq ft per gallon). The coats behind 2 gallons are 2: at 1 coat the need is 1 gallon (20 ft × 12 ft driveway, 240 sq ft, 0.96 gallons a coat, 0.96 gallons exact, 1 coat, 250 sq ft per gallon); at 3 coats it is 3 gallons (20 ft × 12 ft driveway, 240 sq ft, 0.96 gallons a coat, 2.88 gallons exact, 3 coats, 250 sq ft per gallon). The coverage behind 2 gallons is 250 sq ft a gallon: at 200 it is 3 gallons (20 ft × 12 ft driveway, 240 sq ft, 1.2 gallons a coat, 2.4 gallons exact, 2 coats, 200 sq ft per gallon); at 300 it is 2 gallons (20 ft × 12 ft driveway, 240 sq ft, 0.8 gallons a coat, 1.6 gallons exact, 2 coats, 300 sq ft per gallon). Each reverse moves one input and holds the rest, so the step is exactly one dimension, coat or coverage change.

What the defaults assume

The defaults assume a 20 ft by 12 ft rectangular driveway, 2 coats, and 250 sq ft a gallon from the sealer label. They do not assume crack filler, edge prep or a primer coat — a driveway with wide cracks counts its crack filler separately, and the sealer is bought by the gallon, not by the crack.

Who uses this

• A homeowner sealing a driveway: the 2-gallon order settles the store call before the first coat goes down.
• A DIYer resealing a worn drive: the same maths on the driveway alone gives the gallons, not a whole parking lot.
• A contractor quoting a job: driveway size, coats, coverage — the quote follows the same three steps, and the coverage line shows the client why.
• A landlord budgeting a turnover reseal: the driveway size off the listing, multiplied out, gives the sealer line on the turnover budget.

Accuracy & limitations

The arithmetic is exact for the inputs entered; the judgement is the coverage and the coats. Real driveways have cracks, rough patches and edges, and the label on the bucket overrides any planning figure; a driveway measured gross over-orders, and a coverage figure read off a smooth driveway under-orders a rough one. Treat 2 gallons as the planning order for a 20 ft by 12 ft driveway at 2 coats and 250 sq ft a gallon, and allow a third gallon for a driveway cut with cracks and rough patches.

Cite this calculator

Bright Side Kit, “Driveway Sealer Calculator: 2 Gallons for a 20x12 Drive”, https://brightoolbox.com/driveway-sealer-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (20 ft × 12 ft driveway, 2 coats, 250 sq ft per gallon) so the 2-gallon result can be checked.

Frequently asked questions