Miami to Key West in a Day: What the Drive Actually Costs You

By Matt Spaulding · August 29, 2026

Photo: Dori, CC BY-SA 3.0, via Wikimedia Commons

It comes up on every Miami trip: can you drive to Key West and back in one day? You can. A live routing check on August 29, 2026 puts it at 165 miles and 3 hours 41 minutes each way down US-1. Both numbers are true, and neither describes the day you will actually have.

Three hours 41 minutes is the floor, not the drive

That estimate assumes an empty road, and nobody who does this trip for a living plans around it. Gray Line Miami runs it daily on a published schedule: hotel pickup between 6:00 and 7:30am, arrival in Key West around noon, departure back at 5:30pm, and the listing calls the whole thing a 15-hour experience. An operator who has made the run a hundred times budgets five to six hours in each direction, and hands paying guests about five and a half hours on the island.

The road explains it. US-1 through the Keys is largely two lanes with a low speed limit for long stretches, and it carries 42 bridges. There is no passing lane worth the name, so one slow driver sets the pace for everyone behind. At least you know how much road is left: everything down there is addressed by mile marker, counting down from about MM 126 near Florida City to MM 0 in Key West.

The 18-Mile Stretch is the part that can end the plan

Between Florida City and Key Largo, US-1 runs a causeway across the marsh that everyone calls the 18-Mile Stretch, and it is the only road in or out of the Keys at that point. Miami TV stations have covered multi-hour full closures of it after crashes repeatedly over the past several years, in both directions. When it shuts there is no detour. You sit, and a day trip has no slack to absorb that.

One alternate covers the North Key Largo end: Card Sound Road (CR 905), which crosses on a toll bridge at $1.50 for a two-axle vehicle plus $1.00 per additional axle, all-electronic, no cash. Your mapping app will flag the route as having tolls, and that flag is almost certainly the Turnpike's Homestead Extension out of Miami rather than anything in the Keys. The Overseas Highway itself is free.

The Seven Mile Bridge, and the one you get out of the car for

The bridge you are picturing runs from Knight's Key at Marathon to Little Duck Key, mile markers 47 to 40. It is 6.79 miles long, two lanes, and it opened on May 24, 1982. The highway sits on the bones of Henry Flagler's Over-Sea Railroad, finished in 1912 and wrecked by the 1935 Labor Day Hurricane, and in 2009 it became the first All-American Road in Florida. It is a remarkable thing to drive across, and at highway speed you are over it in minutes.

The older bridge alongside is a separate structure, and it is what day-trippers miss. A 2.2-mile section of the original span reopened in 2022 as a walking and cycling path out to Pigeon Key, a small island that once housed around 400 railroad workers and is now a museum. A 60-passenger tram runs it three times a day. You have to park and get out for it, and a noon-to-five day leaves no room.

What the round trip costs before you buy anything

Fuel first. A 330-mile round trip at 27.2 mpg, the EPA's real-world average for model-year 2024 vehicles, works out to roughly 12.1 gallons. Florida's average for regular sat at about $3.92 a gallon on August 29, 2026, so call it $47 to $48 in gas. That is a calculation rather than a quoted price, and your car will move it.

Then parking, at both ends. In Old Town the dependable answer is the city garage at 301 Grinnell Street, open 24 hours, at $6 an hour plus tax with a $48 daily rate as of August 2026. Eight hours on the island hits that number. Meanwhile your Miami hotel is charging for a space your car is not in: valet runs $52 a night plus tax at Kimpton Surfcomber, $58 plus tax at Kimpton EPIC, $65 a day at Four Seasons Hotel Miami.

What five hours on the island actually buys

One real thing, plus wandering. Old Town Trolley is the sensible spine: a 13-stop, roughly 13-mile narrated loop that takes about 90 minutes if you never leave your seat. Start hopping off and it stretches fast, because trolleys reach each stop every 20 to 30 minutes and the last one leaves Mallory Square at 4:30pm.

The efficient pairing sits at Mallory Square, where the Key West Aquarium and the Shipwreck Treasure Museum share one address at 1 Whitehead Street. The aquarium runs guided presentations every 15 to 30 minutes between 9:30am and 5:15pm, all included with admission. The Shipwreck museum takes final entry at 5pm and puts a 65-foot lookout tower over the square. Two stops, one walk, and you park once.

What five hours cannot buy is the water or the sunset. North America's only living coral barrier reef sits about seven miles offshore, so a reef snorkel or the glass bottom boat is a half-day commitment on a fixed departure. And sunset, the thing this island is famous for, lands after any sensible departure. A sunset sail runs two hours, which means driving home well after dark. The rest is on our things to do in Key West page.

If you are driving it, start from the right side of the bay

Downtown Miami puts you on US-1 heading south from the door. From South Beach or Mid-Beach you add a causeway crossing to the front of an already long day, at six in the morning.

Then check the one thing that decides whether a 15-hour absence is painless: in-and-out privileges. Kimpton EPIC gives unlimited in and out on its $58 plus tax valet, and The Elser Hotel Miami does the same on self-parking at $63 overnight, though it also bills a $59 nightly amenity fee. Miami Marriott Biscayne Bay is one of the few downtown properties with a real self-park rate, $45 a day against $50 for valet. The one to watch is W Miami, where the valet is run by Icon Brickell rather than the hotel, priced by the hour, with no in-and-out privileges.

The verdict

It works, and it costs a whole day to get five hours that skip the reef and the sunset. If you are set on it, make it the only plan on the calendar, leave by six, and accept that one crash on the 18-Mile Stretch rewrites the afternoon. Letting Gray Line drive starts at $75, roughly what a solo driver spends on gas and the Grinnell Street garage, though a couple flips that math back.

If the calendar allows, two nights is the practical minimum, which is what our Key West pages already say. That buys a full day for a boat trip, the thing most worth protecting, and an evening you do not have to leave before sunset. We publish attraction pages for Key West and no hotel pages, so the room down there is yours to find.