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Race time predictor

Enter a recent time at one distance and get your predicted 5K, 10K, half marathon and marathon times, with the training paces that go with them. The maths runs in your browser; nothing is sent.

Your predicted times

	Daniels (VDOT)	Riegel	Pace
5K	24:06	23:59	4:49/km
10K	50:00	50:00	5:00/km
Half marathon	1:50:52	1:50:19	5:15/km
Marathon	3:49:34	3:50:01	5:26/km

Your training paces · min/km

Your VDOT

40.0

Easy

6:11–6:49

Threshold

5:05

Marathon

5:26

Intervals

4:40

Repetitions

4:25

The next goal: 10K under 45 minutes →

How it works

Daniels (VDOT): Jack Daniels and Jimmy Gilbert’s formula estimates the oxygen cost of your pace and the share of your VO₂max you can hold for the length of the effort. Their ratio is an index, the VDOT, from which a time at any distance and your training paces follow.

Riegel: Peter Riegel’s formula, T2 = T1 × (D2 / D1)^1.06, extrapolates a time from one distance to another with a single exponent. Simpler, it gets optimistic as the gap between distances grows.

What these numbers don’t tell you

A predicted time is what you could run with training suited to the distance, on a flat course, in cool weather. It knows nothing about hills, heat or how much you train. Use it to pick a goal, not as a promise. This content is for information only and does not replace the advice of a doctor or a coach.

A plan to beat this time

Kardioo starts from your real sessions, works out your paces and builds a plan that adjusts every week to what you actually did. The first week is free.

Coming soon