TransJeju by UTMB
Trans Jeju by UTMB (Jeju 100K)
Jeju City (Jeju World Cup Stadium)
Race guide
Updated 19 July 2026
Trans Jeju by UTMB is a 104km loop that starts and finishes at Jeju World Cup Stadium, climbing from sea level to a high point of 1919m near Hallasan before dropping back to the coast. With 4057m of vertical gain packed into that distance, the profile isn't one big mountain and a long cruise home — it's a steady grind up through the mid-race checkpoints, a summit-area push, and then a long, technical unwind back to the finish. The overnight-into-morning cutoff (Day 10:00+1) tells you this is built to be run through the night, which shapes everything from headtorch planning to how you ration effort in the first half.
The Course & Terrain
The race opens with a real statement: from the 80m start at Jeju World Cup Stadium, the course climbs to 422m by CP1 at just 7km — over 340m of gain in the opening stretch, so there's no easing into this one. From there the terrain settles into a long rolling middle section out to CP4 at 42km (649m), a stretch that covers 35km but gains relatively little net elevation, meaning it's made up of repeated smaller ups and downs rather than one sustained climb. That's where a huge chunk of the race's total D+ is actually banked, quietly, in a section that doesn't look decisive on paper. The defining feature of the course sits between CP4 (42km, 649m) and CP5 in the Hallasan summit area (60km, 716m): this 18km block is where the route reaches its 1919m high point before dropping back down to 716m at CP5. After that, the back half from CP5 to CP7 (83km, 500m) is a long 23km net descent, followed by a short rise to CP8 (91km, 530m) and a final 13km drop back to the stadium finish at 81m. The overall shape is front-loaded with grind, centered on one major altitude swing, and closed out with a long downhill leg into the finish.
Where the Race Is Decided: The Hallasan Push
The block between CP4 (42km, 649m) and CP5 (60km, 716m) is the crux of Trans Jeju. Climbing to the 1919m high point and back down inside those 18km is a far bigger ask than the numbers between the two checkpoints suggest, since CP4 and CP5 sit at almost the same elevation — the real work happens in the middle, out of sight of any checkpoint split. Runners who arrive at CP4 already dug into a time deficit tend to unravel on this climb, because it demands legs that still have a genuine gear left, not just a positive attitude. The smart way to treat this section is as the payoff point for everything banked earlier. If the opening climb to CP1 and the long rolling grind to CP4 have been run with restraint, the Hallasan push becomes an execution problem rather than a survival problem. If they haven't, this is exactly where the accumulated fatigue from those early kilometres catches up — the climb doesn't forgive an early effort that felt fine at the time but wasn't sustainable.
Pacing & Fueling: Why the First Half Is a Deposit
The single biggest lesson to take into this race is that the early kilometres — the climb to CP1, and especially the long 35km rolling stretch to CP4 — feel more forgiving than they are. It's tempting to run them on feel and bank a fast split, but that time isn't free; it's borrowed against the Hallasan climb and the long descent that follows. The proven approach is to run the first half patiently, even conservatively, treating any early speed as a deposit rather than a gain. That patience is what funds a strong closing effort rather than a survival shuffle through CP7, CP8 and the final descent to the stadium. Small issues also compound fast over 104km and an overnight cutoff — a poorly fitted pack, a missed gel, a bottle running low. Fix problems the moment they appear rather than telling yourself it's fine for another few kilometres; a short stop to sort something out early is far cheaper than the same problem multiplying by CP7 or CP8. Break the second half into manageable chunks between checkpoints — CP5 to CP7, CP7 to CP8, CP8 to the finish — and treat each as a planned reset rather than an open-ended slog.
Water, Heat and Margins on the Trail
With crew access only at CP4 (42km) and CP7 (83km), the stretches between checkpoints — particularly the 18km CP4-to-CP5 block over the 1919m high point and the 23km CP5-to-CP7 descent — are where water management matters most. The rule that serves runners well here is simple: don't dump water before the next source is confirmed in hand. On a course with a summit push in the middle and long unsupported miles either side of it, a hydration margin isn't a comfort, it's the thing that keeps the Hallasan climb and the long descent afterward from turning into a crisis. Given the generous but not unlimited cutoff (Day 10:00+1), expect this race to be run through at least one full night, so plan lighting, layers for the 1919m high point, and food around a multi-hour effort rather than a single-session race. Conditions on the exposed summit section can differ sharply from the coastal start and finish, so carrying for both the heat lower down and the cooler, more exposed conditions near the high point is part of running this course sensibly rather than optimistically.
Race Trans Jeju by UTMB (Jeju 100K) with Crux
Get the strategy, fuelling and crew plan dialled for this exact course — built from the real route, climbs and cut-offs. Your first race is free.
Plan this race — freeCourse profile
Checkpoints & cut-offs
✓ Course data verified against the official source (2026-07-05) · official source
0 km · 79 m · Sat 05:00
7.2 km · 414 m · Sat 06:40
20.3 km · 1225 m · Sat 10:40
28.6 km · 975 m · Sat 13:10
40.8 km · 575 m · Sat 15:10
58.5 km · 757 m · Sat 20:40
71.1 km · 456 m · Sat 23:40
82.3 km · 494 m · Sun 04:00
91.8 km · 414 m · Sun 07:00
103.4 km · 81 m · Sun 10:00
More races
More UTMB World Series
More in South Korea
Similar distance (100 km–100 miles)
Racing Trans Jeju by UTMB (Jeju 100K)?
Get a complete race strategy — pacing, fuelling, crew plan and the crux moments — built on this exact course.
Plan your race in Crux →Strava is your training. Crux is your races.