Riegel Race Predictor

Riegel's formula predicts race times based on a recent performance. Adjust the Decay (k) to compare different slowdown assumptions over distance.

Recent Distance

Recent Time

Decay Constant (k)1.06

Lower fade (1.02)Higher fade (1.15)

Standard k = 1.06.
A lower exponent produces less modelled slowdown as distance grows; a higher exponent produces more. This control changes a scenario—it does not classify your physiology.

Predictions

Riegel race predictions
Distance	Predicted Time	Pace
1 Mile	06:01	3:44 min/km
5K	20:00	4:00 min/km
10K	41:42	4:10 min/km
Half Marathon	01:32:00	4:22 min/km
Marathon	03:11:49	4:33 min/km
50K	03:49:38	4:36 min/km
100K	07:58:46	4:47 min/km