The full distance
Ironman is 3800 m swimming, 180 km cycling and 42.2 km running — 226 km in total, or 140.6 miles. The arithmetic is the easy part; the hard part is that each leg is long enough to change how the next one feels. A 20-minute swing on the bike is normal; a 40-minute swing on the run is common.
The cut-offs
Most Ironman races allow 2:20 for the swim, 5:30 to the bike finish (about 8:10 elapsed) and 17 hours total. The calculator gives the finish time, so check it against those limits with a margin. A 16:30 estimate is not a comfortable plan — it is a plan that fails if the wind picks up.
Fuelling is the fourth discipline
An Ironman burns 8,000–10,000 kcal. You cannot replace that, but you can avoid running out: 60–90 g of carbohydrate per hour on the bike, 30–60 g on the run, plus sodium. The calculator cannot model bonking, which is exactly why the estimate should be treated as a best case.
Frequently Asked Questions
What is a good Ironman time?
Finishing is the achievement. Sub-12 hours is a strong age-group result; sub-10 is competitive; the professional race is around 8 hours.
How much does the marathon slow down?
Expect 10–15% slower than an open marathon, and more if the bike was windy or the run is hot.
Can I finish under 17 hours?
Yes, with a swim under 2:00/100 m, a bike around 25 km/h and a run/walk marathon. The run/walk calculator is the practical tool for that plan.
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