The Big Island covers 4,028 square miles, 63 percent of the Hawaiian archipelago's land area, and it drives like it. Two airports sit on opposite coasts about two hours apart. There is one fast road across the middle and one long road around the outside, and neither is quick. These are realistic drive times between the places you will actually go, plus the roads that cost more time than the map suggests.
Kona International (KOA) is on the dry west side. Hilo International (ITO) is on the wet east side. The drive between them takes about 1.5 to 2 hours over Saddle Road. That single fact decides more of your trip than anything else you book. If your lodging is on the Kohala coast and your flight lands in Hilo, you have added roughly two hours to your arrival day and another two to your departure.
Flying into one airport and out of the other works well if you are crossing the island anyway. Before you book that way, check with your rental company whether it allows a one-way drop-off between KOA and ITO and what it charges, rather than assuming it is free.
Saddle Road is Route 200, renamed the Daniel K. Inouye Highway in 2013. It runs 52.7 miles across the middle of the island, passing between Mauna Kea and Mauna Loa, and reaches a maximum elevation of 6,632 feet in the Humuʻula Saddle. Most people still picture the old road: one narrow lane each way, blind rises, no shoulder. That road is gone. Sections were rebuilt and opened in 2007, 2009 and 2013, and Wikipedia's route description records that the entire road is now well paved, with a separate lane for trucks and slower cars on the uphill sections.
Rental companies used to prohibit their cars on Saddle Road. Most now allow it. Read your own agreement anyway, and note that two roads on this island are genuinely restricted no matter what your contract says: Waipiʻo Valley Road is closed to visitors, and the Mauna Kea summit road above the Visitor Information Station is unpaved and requires four-wheel drive in low range.
What has not changed is the crossing itself. It runs high and often through cloud, there is no fuel and nothing open along it, and phone coverage is patchy. Fill up in Waimea, Hilo or Kona first, and download your maps before you leave town.
Kailua-Kona town is a short drive from the airport, on the order of ten to fifteen minutes. Hāpuna and the Kohala resorts are north of the airport, well under an hour. Waimea is roughly an hour inland. Hilo is 1.5 to 2 hours over Saddle Road.
Hawaiʻi Volcanoes National Park is the long one, and here the Park Service publishes the numbers itself: 95 miles southeast from Kailua-Kona on Highway 11, a 2 to 2.5 hour drive, or 125 miles through Waimea and Hilo via Highways 19 and 11, which takes 2.5 to 3 hours. From Waikoloa it is 90 miles southeast on Highway 200, about 2 hours.
Hilo is the closest base to the volcano by a wide margin. The Park Service gives it as 30 miles southwest on Highway 11, a 45 minute drive. Waimea is roughly an hour up Highway 19, and the Waipiʻo Valley lookout is beyond it at the end of the Hāmākua coast.
Hilo also puts you nearest ʻAkaka Falls, the Puna coast and the Hāmākua waterfalls. It is a working town rather than a resort strip, and it rains: Hilo International Airport averaged about 127 inches of rain a year between 1981 and 2010, against about 19 inches at Kailua-Kona over the same period.
The ring is Highway 11 along the south and Highway 19 along the north. People try to drive it in one day. You can, but it is a long day behind the wheel and you see the island through a windshield. For scale, the Park Service puts Kailua-Kona to the volcano at 2 to 2.5 hours going south on Highway 11, and 2.5 to 3 hours going the other way through Waimea and Hilo, and that is before you stop anywhere.
Split it instead. South half one day: Kona, Kaʻū, Hawaiʻi Volcanoes, overnight in Volcano or Hilo. North half the next: Hilo, the Hāmākua coast, Waimea, Kohala. Same ground, and you actually get out of the car.
Mauna Kea Access Road turns off Saddle Road near its high point. It is paved as far as the Visitor Information Station at 9,200 feet and unpaved above that. The University of Hawaiʻi at Hilo, which runs the station, states that drivers are required to use four-wheel drive above the VIS because the summit road is unpaved, rough and steep, that four-wheel-drive low range should always be used to reduce brake failure and overheating, and that you should have at least half a tank of fuel before going up. It also asks that vehicles be free of invasive species and that no muddy vehicles go to the summit. Plan to acclimatise at least 30 minutes at the station before climbing higher.
Waipiʻo Valley Road drops into the valley on a 25 percent average grade, with sections up to 45 percent, and is described as the steepest road of its length in the United States. Access to the valley floor by road is currently allowed only for island residents, county-permitted tour company operators, and people practising Native Hawaiian traditional or customary rights. The lookout at the top is open to everyone. Confirm the county's rule before you plan a day around it.
Kekaha Kai State Park is reached by a rough lava road off Highway 19 and is slow in any vehicle; the gates run 8:00 a.m. to 6:30 p.m. and close at 7:00 p.m. Chain of Craters Road inside Hawaiʻi Volcanoes leads down to the coast and dead-ends there, so everything you drive down you drive back up.
Fuel up before Saddle Road, before the Kaʻū stretch and before the Puna coast. These are the three places on the island where the gap between stations is long enough to matter, and Naʻalehu is the practical stop in Kaʻū.
Do not book a sunset dinner on the day you drive to the volcano. Hawaiʻi Volcanoes is open 24 hours, viewing runs late, and the return to Kona is over two hours in the dark. The Park Service also warns that park parking lots frequently reach capacity by 10 a.m., so an early start or a late one beats mid-morning. Download offline maps before you go, because coverage is unreliable across Saddle Road, the summit road, Chain of Craters Road and the remoter parts of the Hāmākua and Puna coasts.