Race Time Predictor
Predict your finish time at a different race distance, based on a recent result.
Calculate
Enter your values below.
Result
Predicted time
0
Formula used
T2 = T1 × (D2 ÷ D1)1.06 (Riegel's formula)
Example: 25:00 for 5 km → predicted 10 km time ≈ 52:04.
How to use this calculator
- Enter Known finish time (minutes), Known distance (km), Target distance (km).
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
What is Riegel's formula?
A well-known formula for predicting race times at different distances based on a known performance, using a fatigue exponent of 1.06.
How accurate is this prediction?
It's a reasonable estimate for similar distances, but accuracy decreases for very different distances (e.g. predicting a marathon from a 5K).
Does this account for terrain or weather?
No, it's based purely on the time/distance relationship — race day conditions can meaningfully affect actual results.
Can I predict a shorter distance from a longer one?
Yes, the formula works in both directions.