Half Marathon Time Predictor
Predict 13.1 mi via Riegel.
Result
Predicted Half
1:39:21
Pace 7:35/mi.
- Base race6.21 mi in 45:00
- Predicted Half1:39:21
- Pace7:35/mi
Step-by-step
- Riegel formula T₂ = T₁ × (13.109/6.21)^1.06 = 5,961s.
How to use this calculator
- Recent race + time.
- Read prediction.
About this calculator
13.1 mile half marathon predictor. From 10K: most accurate. From 5K: optimistic. From full marathon: conservative. Train with progressively longer runs (peak at 11-13 mi long run) for best half-marathon performance. Most amateur halves: 1:45-2:30. Sub-2:00 is a common amateur goal — equates to ~9:09/mi pace.
Frequently asked
Peak long run: 10-12 mi for half marathon (don't need to do 13 in training). Shorter runs build base.
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