© 2026 PredictMyRun
Enter a recent run and discover your potential across popular race distances. Perfect for planning your next PR!
Tell us about a recent run you've completed, and we'll predict your potential times across popular race distances.
PredictMyRun uses Riegel's formula, a scientifically proven method for estimating running performance across various distances. This formula is widely used by coaches and athletes to set realistic race goals and training paces.
T₂ = T₁ × (D₂/D₁)^1.06
Where T₁ is your known time, D₁ is your known distance, T₂ is your predicted time, and D₂ is your target distance.
Whether you're preparing for your first 5K or targeting a marathon personal best, our predictions help you set achievable and motivating running goals based on your current fitness level.
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The Riegel formula is remarkably accurate for many runners, especially for predicting times between distances that aren't too far apart (e.g., 5K to half marathon). Individual factors like training specificity and race conditions can affect actual results.
For best results, use your most recent race time or time trial as your known performance. The closer your target distance is to your known distance, the more accurate the prediction will be.
While the calculator provides estimates for any distance, it's most accurate for road running distances up to the marathon. Trail running and ultramarathons involve additional variables like terrain, elevation, and pacing strategies that may affect accuracy.
Use the predicted times to set realistic race goals and to establish appropriate training paces for different workouts. Consider these predictions as benchmarks that can help you track progress and identify strengths or weaknesses across different distances.
