Marathon Race Predictor
Enter any recent race result to predict your finish times across all standard race distances.
Enter your recent race time and distance to instantly predict your 5K, 10K, half marathon, and marathon finish times using the Riegel formula — the gold standard for race time prediction.
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About Race Time Prediction
Common Questions
How accurate is the Riegel formula?
The Riegel formula is accurate to within ±5–10% for well-trained runners predicting across similar distances. Accuracy decreases with large distance gaps (e.g. 5K to marathon) or when the input race was not run at maximum effort.
What is the Riegel formula?
T2 = T1 × (D2/D1)^1.06, where T1 is your known finish time, D1 is the known distance, D2 is the target distance, and T2 is the predicted time. The exponent 1.06 accounts for the increasing effect of fatigue over longer distances.
Can I predict a marathon from a 5K?
Yes, but the prediction will be less accurate. The formula works best with input races closer to the target distance. For marathon prediction, a recent 10K or half marathon result will give the most reliable estimate.
What is a good marathon finish time?
Beginner: 4:30–5:30 | Intermediate: 3:30–4:30 | Advanced: under 3:30 | Elite: under 2:30. The average marathon finish time is around 4:30 for men and 4:55 for women.
How do I use this to pace my race?
Use the pace column for your target distance to set your per-kilometer strategy. For example, if your predicted marathon pace is 5:30/km, aim to run the first half slightly slower (5:35/km) and negative split the second half.
Steps For
How to predict your marathon time
Enter a recent race distance and time to predict your finish time for a marathon (and 5K, 10K, half).
- 1
Enter a known race distance and time
Use a recent, hard effort — 5K, 10K, half marathon, or any distance you've raced recently.
- 2
Read your predicted times
Using the Riegel formula, the calculator predicts your finish times for 5K, 10K, half marathon, and marathon distances.
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