Calcvers
Finish Time Calculator
Running
Generated
September 24, 2026
Predicted finish time
1:39:17
4:42 /km for 21.1 km
Your inputs
- Recent race distance
- 10 distance
- Unit
- Kilometres
- Time — hours
- 0 h
- Minutes
- 45 min
- Seconds
- 0 s
- Predict time for
- Half marathon
Breakdown
- Target distance
- 21.1 km
- Required pace
- 4:42 /km
- Based on
- 10km
Predicted times across distances
| Item | Value |
|---|---|
| 5K | 21:35 |
| 10K | 45:00 |
| Half marathon | 1:39:17 |
| Marathon | 3:27:01 |
What this means
This uses Peter Riegel's endurance formula, which models how finish time grows with distance using an exponent of 1.06. Feed it one honest recent result and it predicts your times at other distances remarkably well — most accurate when your target isn't wildly longer than your input race.
Recommendations
- Use a recent, hard, well-paced effort as your input for the best prediction.
- Treat the longer predictions as goals that require specific endurance training to actually hit.
Watch out
- Predictions assume similar terrain, conditions and — crucially — that you've trained for the target distance. Jumping from 5K fitness to a marathon time won't hold without the long runs.