IRONMAN 70.3 Boulder 2026
A reservoir swim, two rolling loops under the Flatirons, and a two-lap run on hard-packed dirt. All of it at 1,600m of altitude.
This edition has passed
The next edition usually opens entries shortly after race day. Set the target early: the best training blocks are the ones with a real date at the end.
Building for this one? 70.3 training plan covers the sessions, the weekly shape and how the block is paced. The R.A.C.E. Framework explains why it is built that way.
“Boulder sits at about 1,600 metres and altitude is the whole story. Arrive either three days out or three weeks out, never one week out, and take your goal power down by five to eight percent whatever the profile says.”
The race
The course
No course maps for this race. IRONMAN publishes no downloadable route for any leg of this race, only a live tracker that runs on race day, so there is nothing to draw a course map from. Everything below comes from the official course page, checked on the date at the foot of this section.
One counterclockwise loop, entering at the east boat ramp and exiting at the west before heading to transition.
Two loops from the reservoir onto the Diagonal Highway towards the Foothills Highway, short rollers, then right onto rural Hygiene Road and a fast downhill run to 63rd Street before rejoining the Diagonal for the second lap.
Two counterclockwise loops around the reservoir, part trail, part hard-packed dirt road on Monarch and 55th, with downhill rollers. This is the ground the best distance runners in America train on daily.
Not yet confirmed for this edition: bike elevation gain, transition locations, cut-off times, water temperature history. We publish these only once they are on the official course page, so check there before you pace off anything here.
Course details verified against the official IRONMAN 70.3 Boulder course page on 14 August 2026. Courses change; the official page is always the last word.
Questions, answered
When is IRONMAN 70.3 Boulder 2026?
What distances can I race at IRONMAN 70.3 Boulder?
How hard is the course?
What is the swim like?
How long do I need to train for it?
How do I enter?
Read before you race
Race Week Is Where People Unravel.
More races like this
Photograph of Boulder, Colorado, USA: Jeffrey Beall, CC BY 4.0, via Wikimedia Commons. Not official race photography.
This listing is for information only. Unbroken is not affiliated with, endorsed by, or sponsored by IRONMAN 70.3 Boulder or its organiser. Details are based on publicly available information; names are used descriptively to identify the event. For accurate, up-to-date information and to enter, always use the official event website.