Free tool

Pace calculator: how fast will you run?

Enter one of your results and see the prediction for 5 km, 10 km, the half marathon and the marathon, with the pace per kilometre.

Your time

Formula: Pete Riegel, 1981. What it tells you and what it does not – below and in the article How fast will you run the Riga marathon?

How to read the result

For example, a 10 km result of 45:00 means a half marathon of 1:39:17 and a marathon of 3:27:01. The second number is only true if you have trained for the marathon.

A prediction, not a promise

Formula: time × (new distance ÷ old) to the power of 1.06. It assumes you are trained for each distance – it calculates what you could run if you had trained for it.

The longer the distance, the bigger the “if”

From 5 km to 10 km the prediction is usually close. From 5 km to the marathon it is an estimate: long runs, fuelling and the weather decide there, and the formula sees none of it.

Pace zones live in the plan, not here

The calculator tells you where you are today. Training paces – easy, tempo, intervals – depend on experience, goal and weekly volume, and Jānis writes them into the plan.

Questions about the prediction

How accurate is the prediction?

It is a statistical formula, not a measurement. It comes close if you have trained for that distance and the result you start from is recent – from the last couple of months. The further the distance from the one you entered, the bigger the error.
Which distance should I predict from?

From the nearest one. A half marathon is better predicted from 10 km than from 5 km, a marathon from a half. If you have several results, use the one closest to the target distance and most recent.
Why does the marathon prediction look too fast?

The formula assumes you are trained for the marathon. If your longest run was 10 km, it shows a time you will not reach yet – not because you are slow, but because the endurance is not built yet. In a marathon the long runs, fuelling and the pace of the first half decide.
Does the calculator give training paces?

No. Easy, tempo and interval paces depend on experience, goal and weekly volume, so the coach sets them in the plan, not a formula. The calculator tells you where you are today; the plan tells you what to do tomorrow.

And how do you get there?

The prediction tells you where you are today. A training plan tells you what to do tomorrow, with pace zones built for you. If you would rather talk first, there is a video consultation.

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