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Race time predictor
What a result at one distance says about another, by two formulas that disagree
It runs entirely in this browser tab: your times, weights and training are never uploaded, and the tool makes no network request while it works. Open your browser's network panel and try it — nothing leaves the page.
Settings
- Distance unit
- Declared rather than guessed: the same run is 5:00 a kilometre and 8:03 a mile. Choices: km, mi.
- Riegel exponent
- In hundredths. The published 1.06 was fitted to records and runs long for everybody else. A number from 100 to 120.
How to use it
- Paste your text into the box above, or open a file.
- Adjust the settings beside it until the result is what you wanted.
- Copy the result, or save it as a file. The result updates as you type.
Questions
- Which unit are the distances in?
- Whichever one you set. Kilometres and miles are both here and the setting says which, because a pace is per unit: the same run is 5:00 a kilometre and 8:03 a mile, and a tool that guessed would be wrong by 61 per cent in a way that looks entirely plausible.
- Why does the race predictor show two answers?
- Because Riegel and Cameron disagree by minutes over a marathon and neither of them knows whether you have run the mileage. The spread between them is the honest answer; a single number would be a claim nobody can make. Riegel's exponent is a setting for the same reason — the published 1.06 was fitted to world records.
- Is this training advice?
- No. The paces and zones come from published tables fitted to a population, and every one of them is a band rather than a boundary — the number is where to start. The workout plan is a template that knows nothing about your history or your injuries, and it says so.
- Is what I type uploaded anywhere?
- No. This page carries the whole tool as WebAssembly and runs it on your own device. A race time is a person, a body weight is a person, and a training log says where somebody lives and when they are out running; none of it is sent anywhere.
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