Running Pace & Race Time Predictor
Calculate your running pace, finish time, or required distance. Predict race times for 5K, 10K, half marathon, and marathon.
Not needed for Race Time Predictor mode
e.g. 5.5 = 5 min 30 sec per km
e.g. 55 = 55 minutes | 90 = 1 hour 30 min
For Race Time Predictor only
Your recent finishing time in minutes
How to Use This Calculator
Mode 1: Finish Time
Enter your target distance and pace (min/km) to calculate your finish time.Mode 2: Pace
Enter your distance and total time to find out your pace per km.Mode 3: Race Time Predictor
Enter a recent race result and predict equivalent performances at other distances using the Riegel formula.Pace Reference:
Formula
Riegel Formula: T₂ = T₁ × (D₂/D₁)^1.06 | Pace = Time / DistanceFrequently Asked Questions
How accurate is the race time predictor?
The Riegel formula is accurate to within 1–5% for most runners at distances within 2–3x of their reference race. It assumes equal training and conditions. Predictions for the marathon from a 5K are less reliable.
What is a good 5K time?
For recreational runners, under 30 minutes is a solid goal. Under 25 minutes is competitive. Sub-20 min is fast (top ~10% of parkrun finishers). Elite runners go under 15 minutes.
How do I enter pace in decimal format?
Enter minutes as a decimal. 5 minutes 30 seconds = 5.5. 6 minutes 45 seconds = 6.75. Think of it as minutes + (seconds/60).
What is a negative split?
Running the second half of a race faster than the first. It's the most efficient pacing strategy for distance races — start conservatively and finish strong.
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