Mauna Kea climbs 42.3 miles (68.1 km) at an average of 6.2% from Hilo, on the Pacific, to the 13,780 ft (4,200 m) summit, with 13,766 ft (4,196 m) of climbing and barely any downhill. Climb databases rank it as the hardest bike climb on the planet, and not because of the average: the last 14.3 miles (23 km), on the summit access road, average 9.5% starting from 6,562 ft (2,000 m) of altitude.
What the climb is like
- Hilo to Saddle Road (mile 0-28 or so). You leave on Waianuenue Avenue through humid rainforest and join Route 200 (Saddle Road). About 19.9 miles (32 km) of it carry fast traffic, trucks included, though the shoulder is very wide.
- Access road to the visitor center (mile 28-34, from 6,588 to 9,423 ft / 2,008 to 2,872 m). You turn toward the summit and the gradient shoots up. The Onizuka visitor center sells sandwiches, water and sports drinks. It’s your last stop.
- The dirt section (mile 34-38.8, to about 11,877 ft / 3,620 m). Roughly 4.7 miles (7.6 km) of very steep dirt and sand, where many riders have to get off and push.
- The paved finish (to 13,780 ft / 4,200 m). Ramps up to 15% and a sign warning of 17%, among the observatories in a bare lava landscape.
Climbfinder gives 42.3 miles (68.1 km) and 13,766 ft (4,196 m); PJAMM, 42.5 miles (68.4 km) and 13,753 ft (4,192 m). Both agree on a steepest pitch of 15.2% over 100-400 m.
Permits, closures and altitude
To ride above the visitor center you have to register there (Hawaii state rules require written permission) and stay on the road. Cars need four-wheel drive above that point, so if you want a support vehicle you’ll have to rent one. The summit road sometimes closes for snow, ice or storms: PJAMM reported a closure after the August 2026 storms. Check conditions with the Center for Maunakea Stewardship before you travel.
Altitude is the big problem. At the top there’s about 40% less oxygen than in Hilo, and altitude sickness is common above 8,200 ft (2,500 m). If you live near sea level, spend several days on the island before you try it, climb slowly and turn around if you get a bad headache, nausea or dizziness. In Hilo it’ll be around 68 °F (20 °C) and probably raining; at the top it can snow. The mountain is sacred to Native Hawaiians: respect the marked areas.
What gearing to use
You need mountain bike gearing: a 30-32 chainring with a 40-tooth cog or larger for the dirt section and the final ramps above 12,500 ft (3,800 m). Work out your cadence in the gear calculator. If you want something more manageable in Hawaii, Haleakala on Maui climbs about 10,000 ft (3,000 m), all on pavement.
Frequently asked questions
How long does it take to climb Mauna Kea by bike?
A 159 lb (72 kg) rider on a 21 lb (9.5 kg) bike takes about 5 h at 3 W/kg (216 W), 5 h 55 min at 2.5 W/kg and 3 h 52 min at 4 W/kg. That's an optimistic estimate: the dirt section and the lack of oxygen above 11,500 ft (3,500 m) will slow you down a lot.
Do you need a permit to bike up Mauna Kea?
Yes. Hawaii state rules require written authorization: before continuing above the visitor center (9,423 ft / 2,872 m) you must fill out a registration form and hand it to a ranger or drop it in the box.
What bike do you need for Mauna Kea?
A gravel bike with 40 mm or wider tires, or a switch to a mountain bike for the 4.7 miles (7.6 km) of dirt and sand above the visitor center. You'll need very low gears.