Race Time Predictor
Predict your race times for different distances based on a recent race performance. Uses the proven Riegel formula.
How Does the Race Time Predictor Work?
Our race time predictor uses the Riegel formula, a proven mathematical model that predicts race performance across different distances. The formula accounts for the fact that runners cannot maintain the same pace as distance increases.
Simply enter your recent race time for any distance, and the calculator will predict your potential finish times for 5K, 10K, half marathon, and marathon distances. These predictions are most accurate when:
- Your recent race was run at maximum effort
- You're predicting a distance within 2-3x of your input
- Your training is appropriate for the target distance
- Race conditions are similar (weather, terrain, etc.)
Understanding Your Predictions
Conservative Estimates
The Riegel formula tends to be conservative for shorter distances (5K/10K) if your recent race was a marathon.
Training Matters
Predictions assume proper training. A 5K PR doesn't guarantee marathon success without appropriate mileage.
Use as a Guide
These predictions are starting points. Consider your current fitness, training volume, and race-specific preparation.
Recent is Better
Use your most recent race time for the most accurate predictions. Older results may not reflect current fitness.
Typical Race Time Progressions
Here are some example race time progressions for different ability levels:
| Level | 5K | 10K | Half | Marathon |
|---|---|---|---|---|
| Elite | 15:00 | 31:00 | 1:08:00 | 2:25:00 |
| Advanced | 20:00 | 42:00 | 1:32:00 | 3:15:00 |
| Intermediate | 25:00 | 52:00 | 1:55:00 | 4:00:00 |
| Beginner | 35:00 | 1:13:00 | 2:40:00 | 5:30:00 |
Scientific Basis
The Riegel formula used in this calculator is based on decades of peer-reviewed research in exercise physiology and has been validated across millions of race performances worldwide.
Original Research
Riegel, P. S. (1981). "Athletic records and human endurance." American Scientist, 69(3), 285-290.
Dr. Peter Riegel first established the power law relationship for running performance, proposing that race time increases proportionally to distance raised to the 1.06 power. This mathematical model accounts for the physiological reality that runners cannot maintain the same relative intensity as distance increases.
Large-Scale Validation Study
Vickers, A. J., & Vertosick, E. A. (2016). "An empirical study of race times in recreational endurance runners." BMC Sports Science, Medicine and Rehabilitation, 8(1), 26.
This landmark study analyzed 1.8 million marathon performances to validate the Riegel formula. Researchers confirmed that the exponent of 1.06 is highly accurate for recreational runners, with predictions typically within 3-5% of actual race times. The study found the formula works best when predicting distances within 2-3x of the input distance.
Elite Runner Analysis
Karp, J. R. (2007). "Training characteristics of qualifiers for the U.S. Olympic Marathon Trials." International Journal of Sports Physiology and Performance, 2(1), 72-92.
Research on elite athletes shows the Riegel formula remains accurate across ability levels. Elite runners may have exponents closer to 1.05, while recreational runners cluster around 1.06-1.08, reflecting differences in training adaptation and fatigue resistance at longer distances.
Scientific Validation
Multiple peer-reviewed studies spanning over 40 years have validated the Riegel formula's accuracy. The formula is based on fundamental principles of exercise physiology including VO2 max limitations, lactate threshold, and running economy. It accounts for the mathematical relationship between aerobic capacity and sustainable pace over different distances.
Train Smarter for Your Goal Race
Now that you know your target time, get a personalized training plan designed to help you achieve it. Our AI creates a custom schedule based on your goals, fitness level, and availability.
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