Race Time Predictor (Riegel Formula)
Project any race time from a recent result with Riegel's exponent — and the training caveat that goes with it.
Riegel's 1.06 exponent says pace decays ~6% per doubling of distance — accurate between adjacent distances, optimistic for 5K→marathon jumps because it assumes marathon-grade endurance training. Predicting *up* in distance, add a grain of salt proportional to your weekly mileage honesty.
Formula
For general information only — not medical or training advice. Estimates vary between individuals; consult a qualified professional before changing your exercise or nutrition routine.
Project any race time from a recent result with Riegel's exponent — and the training caveat that goes with it. The Race Time Predictor (Riegel Formula) is a free, private race time predictor tool — every result computes instantly in your browser with no sign-up and no data upload.
About Race Time Predictor (Riegel Formula)
Riegel's 1.06 exponent says pace decays ~6% per doubling of distance — accurate between adjacent distances, optimistic for 5K→marathon jumps because it assumes marathon-grade endurance training. It applies T₂ = T₁ × (D₂ ÷ D₁)^1.06 (Riegel 1981). Use the Race Time Predictor (Riegel Formula) to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Race Time Predictor (Riegel Formula)
- 1Enter your details in the Race Time Predictor (Riegel Formula) input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Race Time Predictor (Riegel Formula)?
- ✓Instant race time predictor result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Riegel PS, American Scientist 1981 — athletic records and human endurance)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Race Time Predictor (Riegel Formula) work?+
Riegel's 1.06 exponent says pace decays ~6% per doubling of distance — accurate between adjacent distances, optimistic for 5K→marathon jumps because it assumes marathon-grade endurance training. The calculation uses the formula: T₂ = T₁ × (D₂ ÷ D₁)^1.06 (Riegel 1981). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Race Time Predictor (Riegel Formula) accurate, and what is it based on?+
The method is traceable to authoritative sources: Riegel PS, American Scientist 1981 — athletic records and human endurance. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Race Time Predictor (Riegel Formula) free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general fitness information only, not medical or training advice. Consult a professional before changing your routine.
What can I use the Race Time Predictor (Riegel Formula) for?+
It's commonly used for race time predictor, riegel formula, marathon prediction. Project any race time from a recent result with Riegel's exponent — and the training caveat that goes with it.
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