Pick a known race
Choose a standard distance or enter a custom one you recently raced.
Race Time Predictor
Enter a recent race distance and finish time to predict your times for 5K, 10K, half marathon and marathon using the Riegel formula.
How it works
Enter your time
Add your actual finish time for that race.
See your predictions
Get instant predicted times for the other standard race distances.
FAQ
How does race time prediction work?
This uses the Riegel formula: predicted time = known time × (predicted distance ÷ known distance)^1.06. It estimates how your endurance scales to longer or shorter races.
How accurate are these predictions?
Riegel predictions are a useful estimate but assume similar training and conditions across distances. Actual results vary with pacing, terrain, weather and how well-trained you are for each distance.
Can I use a custom race distance?
Yes. Select Custom, enter your distance in kilometers or miles, and enter your finish time to get predictions for 5K, 10K, half marathon and marathon.