Finish Time Predictor
Given one race you've done, what should you expect at another distance? Enter a recent result and get predicted times across 1 mile, 5K, 10K, 15K, half marathon, and marathon — the same run-leg distances that make up a sprint, Olympic, 70.3, or Ironman triathlon.
Your recent result
Enter one race you've done recently — we'll predict every other distance from it.
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How this calculator works
Riegel's formula (T2 = T1 x (D2/D1)^1.06) scales a known finish time to a new distance using a fixed exponent of 1.06, derived from real-world race performance across distances.
Assumptions
- • A single fixed exponent (1.06) applies to all distances and athletes
- • The input result reflects a genuine, well-paced effort
Limitations
- • Most reliable between roughly 3.5 minutes and 4 hours of effort
- • Does not account for training history, terrain, or weather
Who this is for
- • Runners and triathletes who want a quick estimate at a new distance from a recent race
- • Athletes choosing a realistic goal time before entering a race
Who this is not for
- • Predicting marathon or Ironman-run-leg times with high precision — the model over-predicts long efforts for runners without matching endurance
- • Course-specific predictions (hills, heat, altitude are not modelled)
References
This tool predicts a finish time from a single result — it isn't a race-day plan. For splits, pacing bands, and a fueling plan built from your own training numbers, use the Race-Day Planner.
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<p><a href="https://mytriathloncalculator.com/calculators/finish-time-predictor?utm_source=embed" target="_blank" rel="noopener">Free triathlon calculator</a> via mytriathloncalculator.com</p>