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Breno Melo
Full Ironman 140.6 Predictor

Predict your full Ironman finish time.

Enter sustainable training paces for swim, bike, and run and we'll model realistic splits plus transitions for the full 140.6 distance. Toggle metric or imperial. Numbers update live.

Units
Race-day conditions
Course profile
Temperature
Humidity
Predicted 140.6 finish
11:15:56
Swim 3.8 km
1:12:50
T1
6:00
Bike 180 km
6:00:00
T2
5:00
Run 42.2 km
3:52:06

How to enter race-realistic paces

  • Swim: use your CSS pace, not a 100m max effort. Add 3–5 sec/100m if it's a non-wetsuit swim.
  • Bike: the speed you can hold at ~65–70% of FTP for 5–6 hours on race terrain. Most age groupers overestimate this by 1–2 km/h.
  • Run: open marathon pace + 30–60 sec/km (or +48–96 sec/mi) for off-the-bike fatigue. Expect walking aid stations after km 25.

What a "good" Ironman time looks like

  • Sub-15h: respectable first-timer. Roughly 50th–70th percentile age-group.
  • Sub-12h: strong age-grouper, top 25–35%.
  • Sub-10h: top 5–10%; many slots Kona-qualify here.
  • Sub-9h: elite age-group / podium territory.

Racing a 70.3 first?

Use the Half Ironman predictor for 1.9 / 90 / 21.1 km splits.

Open 70.3 Predictor
Related calculators

Half Ironman (70.3) predictor

Sister calculator for the 70.3 distance — transitions baked in.

AI race-day nutrition plan

Carbs/hr, sodium and fluid plan for a full IRONMAN — personalized.

Carb loading calculator

Race-week carb load for a 9–15 hour day without GI distress.

Sweat & sodium calculator

Bottle-by-bottle hydration plan for the bike + run.

Want a coach to apply this?

Triathlon coach

1:1 IRONMAN coaching from a coach who has built and raced the distance.

Online triathlon coach

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70.3 coach

Stepping stone block — sharpen 70.3 before the full.

Breno Melo, endurance coach, BostonBreno MeloHead Coach · USA Triathlon, Road Runners Club of America, TrainingPeaks
Published · Last reviewed by Breno Melo
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Methodology and assumptions

Full-distance split projection from standalone ability

Swim 3.8 km from CSS; bike 180 km from FTP at an assumed intensity factor of 0.65–0.72;
run 42.2 km from a heavily de-rated marathon pace; plus transitions and aid-station time.
What it assumes
  • Durability at eight-plus hours, which no short-course test measures.
  • Fuelling of 60–90 g carbohydrate per hour is executed successfully.
Known limitations
  • The full-distance run de-rating is the least reliable number on this site: real variance between athletes is enormous.
  • Heat, GI failure and pacing errors dominate the actual result far more than fitness inputs.
Validated on

Not externally validated. Stated as a planning range rather than a prediction.

Verification

Formula, constants and cited sources last verified on . Spotted something wrong? Email breno@brenoamelo.com and it gets corrected and dated.

How the Ironman prediction is calculated

The bike leg is solved at an intensity factor appropriate to a full day rather than at threshold, because riding above roughly 72% of FTP reliably destroys the marathon.

The run penalty grows with bike intensity and with predicted finish time — the longer the day, the larger the gap between open and off-bike pace.

Transitions and aid-station time are included, which typically add 8-15 minutes over the day.

Sources

References

Every physiological claim on this page traces to one of the primary sources below — the original paper, textbook or governing-body standard, not a secondary write-up.

  1. 01Daniels J (2021). Daniels' Running Formula, 4th edition. Human Kinetics, Champaign, IL. ISBN 978-1-4925-7443-2
  2. 02Allen H, Coggan AR, McGregor S (2019). Training and Racing with a Power Meter, 3rd edition. VeloPress, Boulder, CO — defines FTP and the seven-level power training zones. ISBN 978-1-937715-93-4
  3. 03Wakayoshi K, Ikuta K, Yoshida T, et al. (1992). Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer. European Journal of Applied Physiology 64(2):153–157. doi:10.1007/BF00717953
  4. 04Jeukendrup AE (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine 44(Suppl 1):S25–S33. doi:10.1007/s40279-014-0148-z
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Using this page in your own work?

Copy a formatted reference below. If you are quoting a number from this page, please link back to it so readers can check the source and the date it was last reviewed.

Breno Melo, "Ironman Time Predictor — Breno Melo Endurance Coaching", Breno Melo Endurance Coaching (last reviewed 18 May 2026). https://www.brenoamelo.com/calculators/ironman-time-predictor

Frequently asked
How accurate is a full Ironman time predictor?

Within roughly 7-10% if you input race-realistic paces: swim CSS, bike speed sustainable at 65-72% of FTP, and open-marathon pace plus 30-60 seconds per kilometre for accumulated fatigue off the bike.

What are the full Ironman distances?

3.8 km (2.4 mi) swim, 180 km (112 mi) bike and 42.2 km (26.2 mi) run - 140.6 miles in total.

How long do transitions take in a full Ironman?

Age-group athletes typically take 5-8 minutes for T1 and 4-6 minutes for T2, because long-course transitions include changing tents. The default here is 6 minutes T1 plus 5 minutes T2.

What is a good Ironman finish time?

Sub-12 hours is a strong age-group finish and sub-10 hours is competitive, often around Kona-qualifying territory depending on race and age group.

Why is my predicted run so much slower than my open marathon?

Because 180 km of riding empties glycogen and loads the same muscles you are about to run on. The model applies a fatigue penalty that grows with bike intensity - ride harder and the run penalty gets bigger.

How should I pace the bike leg?

For most age-groupers, 65-72% of FTP as normalized power. Above that the marathon degrades faster than the bike split improves, which is the single most common way an Ironman day falls apart.

Related reading

The 24-Week Ironman Build

What a full-distance block looks like from base to taper.

Fueling the Long Ride

Bottle-by-bottle fueling for four hours and up.

Marathon Fueling Strategy

Carbs per hour, gel timing and the gut training that makes it work.

The Heat Acclimation Protocol

Ten to fourteen sessions that buy back the pace heat takes away.

Free download

24-week Ironman roadmap summary

The full 140.6 build on one page: phase-by-phase volume, the key sessions in each block, and the taper that gets you to Kona-day fresh.

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