IRONMAN Boulder
Boulder sits at roughly 1,650 metres above sea level, and the bike course goes higher. That single fact reshapes the whole race: at this altitude you will produce less power at the same effort, your heart rate will run higher for a given pace, and no amount of sea-level fitness fixes it in the few days you are there.
The 1,900 m swim is in the reservoir, cool and usually calm at dawn. The 90 km bike heads out with the Front Range on your shoulder, and the 21.1 km run finishes on Boulder's paths and roads, largely exposed.
Arrive well ahead of race day or arrive the night before. The middle option, three or four days of acclimatisation, is the worst of both worlds physiologically.
The sun at altitude is also stronger than the temperature suggests. Sunburn on the bike is one of the most common reasons people run badly here.
Who it's for
Built for experienced triathlon athletes.
Good fit if you…
- are experienced in triathlon and want a hard race
- want a well-known, high-status race
Maybe not if you…
- are brand-new to triathlon: start with something shorter
What should you know about IRONMAN Boulder?
- Date
- Saturday, 12 June 2027
- Format
- Half / 70.3
- Water temp
- 19.2°C · 67°F
Need to know
When is IRONMAN Boulder 2027?
IRONMAN Boulder takes place on Saturday, 12 June 2027. Dates can move year to year, so confirm the exact day on the official race page before you book travel.
How do you register for IRONMAN Boulder?
Where does IRONMAN Boulder take place?
Boulder, United States
When has IRONMAN Boulder taken place before?
FAQs
What do athletes ask about IRONMAN Boulder?
Where is IRONMAN Boulder held?
IRONMAN Boulder is held in Boulder, the United States in the CO region. The race page has the venue location and a map, and links straight through to the official site for the precise start area.
What distances can you race at IRONMAN Boulder?
IRONMAN Boulder offers Half / 70.3. The Half / 70.3 is a 1.9 km swim, 90 km bike and 21.1 km run. Pick your distance and enter on the official site. Each format usually has its own start wave and cut-offs.
How hard is IRONMAN Boulder?
IRONMAN Boulder is rated competitive (4/5) for difficulty on FindMyNextRace, based on its distance, terrain, and the level of the field. Use that as a guide and match it to your current fitness before you commit.
How do I enter IRONMAN Boulder?
You enter IRONMAN Boulder through the official organiser. Registration is handled on their site, and FindMyNextRace links you straight there. Places for popular editions can sell out early, so register as soon as entry opens.
Is IRONMAN Boulder part of a race series?
Yes, IRONMAN Boulder is part of the IRONMAN series. Series events often share a qualification, points, or championship pathway, so if you're chasing the series, check how this race fits its calendar.
How should I train for IRONMAN Boulder?
Training for IRONMAN Boulder depends on your target distance and current fitness. Most athletes follow a structured block of 12–20 weeks for a Half / 70.3 effort. Build a plan tailored to your race date and level with AI Training Plan (https://aitrainingplan.app).
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