1K
Your goalCalculate to compare
Health
Race Time Predictor
Turn a recent performance into a race goal and see how reliable that reference is.
Publicidad
Predictions for popular distances
Compare how time and pace change using the same reference performance.
1 mile
Your goalCalculate to compare
5K
Your goalCalculate to compare
10K
Your goalCalculate to compare
15K
Your goalCalculate to compare
Half marathon
Your goalCalculate to compare
Marathon
Your goalCalculate to compare
How to interpret the prediction
Riegel adjusts the expected pace between distances, but it cannot account for your training or race-day conditions.
Comparable performance
A recent, all-out race usually provides a more useful reference than a controlled training effort.
Similar distances
Uncertainty increases when the target distance is very different from the reference distance.
Pace is not constant
The formula accounts for expected fatigue. Use the running pace calculator for exact pace conversions or splits.
Formula used
The central prediction uses a Riegel exponent of 1.06 and retains full internal precision.
Target time = reference time × (target distance ÷ reference distance)1.06. The scenarios use exponents of 1.03, 1.06, and 1.09 to show different levels of performance retention.
Frequently asked questions
What is the Riegel formula?
It is a model that estimates your time for another distance from a known performance. It accounts for the fact that pace usually slows as distance increases.
How accurate is the prediction?
It is a mathematical estimate, not a guarantee. It is generally more useful when your reference performance is recent, represents an all-out effort, and is close to your target distance.
Can I predict a marathon time from a 5K?
Yes, but uncertainty is high. Marathon-specific training, endurance, and nutrition have a much greater effect over that distance.
Why is the predicted pace slower for longer distances?
The formula accounts for the increasing difficulty of maintaining the same pace as distance rises.
Which performance should I use as a reference?
Use a recent race or all-out effort, ideally over a distance and in conditions similar to your goal event.
Does the calculator account for weather, terrain, or elevation?
It does not adjust for them automatically. You can indicate whether conditions were comparable to better understand the uncertainty.
How is this different from the running pace calculator?
The running pace calculator assumes a constant pace. This calculator uses a performance model to estimate how pace changes across distances.