Free tool

5K time predictor

A longer race in. Your 5K out.

Type a recent longer race result. We project your 5K finish using the Riegel formula. Reverse-prediction: longer races slightly overestimate 5K speed.

What did you run?
Units
1
Distance
Pick a preset or type any distance.
km
Quick distances:
2
Finish time
Hours, minutes, seconds.
Hours
Minutes
Seconds
Examples
Marathon
3:50:01
Predicted finish at Marathon

From 10K in 50:00, here are your projected race times.

Find Marathon races →
Predicted race times
5K
23:59
10K
50:00
15K
1:16:51
Half marathon
1:50:19
Marathon
3:50:01
50K
4:35:21

Common 5K predictions

Reference table — popular race times and the Riegel-projected 5K. Predicting 5K from a marathon is rough; from 10K is reasonable.

Input race resultPredictedNotes
10K 40:005K ~19:18Sub-20 target.
10K 50:005K ~24:09Solid sub-25.
Half 1:30:005K ~19:21Sub-20 territory.
Half 1:45:005K ~22:35Sub-23 base.
Marathon 4:00:005K ~24:50Caveat: long-to-short prediction is rough.
More distance predictors & guides
What is a good 5K time?10K time predictorHalf marathon time predictorMarathon time predictorUltra time predictorGeneral race time predictor