Marathon Pace & Race-Time Predictor
Work out your pace, speed and per-kilometer splits — or take one recent result and predict your 5K, 10K, half and full marathon times.
| Split | Cumulative |
|---|
Enter one recent race result. We project your equivalent times at every other distance with Riegel's formula.
| Race | Predicted | Pace/km |
|---|
Estimates assume comparable training and conditions — real results vary with course, weather and distance-specific preparation.
How is pace calculated?
Pace is simply time divided by distance. This tool also converts it to min/mile and km/h, then breaks your race into per-kilometer splits so you can plan an even effort from the gun.
How does the predictor work?
It uses Riegel's formula: T2 = T1 × (D2 / D1)^1.06. It's a well-known endurance model — accurate for similar effort levels, less so when jumping from very short to very long distances without specific training.
FAQ
- How are the finish-time predictions calculated?
- With Riegel's endurance formula T2 = T1 × (D2/D1)^1.06 from one known result, giving equivalent 5K, 10K, half and full-marathon times.
- What pace do I need for a sub-4 marathon?
- About 5:41 per kilometer held evenly for 42.195 km. The table shows the per-kilometer pace for every target time.
- Even split or negative split?
- For most runners an even or slightly negative split beats starting fast. Passing halfway much quicker than target pace is the classic cause of a late-race fade.