Complete guide
Race Time Predictor: formula, example and decision guide
Project an equivalent race time with the Riegel endurance equation. The result updates instantly and keeps every assumption visible.
What the Race Time Predictor measures
Project an equivalent race time with the Riegel endurance equation.
Use the result to compare scenarios built from the same definitions and time period.
Formula and variables
The calculator applies target time = known time × (target distance ÷ known distance)^exponent. Each variable is entered in a labeled field and remains visible beside the answer.
target time = known time × (target distance ÷ known distance)^exponentWorked example
A 25-minute 5K predicts about 52.04 minutes for 10K at exponent 1.06.
Change one input at a time to see which assumption has the greatest effect on the result.
How to interpret the result
Read the main result together with the detailed rows; the headline number alone does not describe every cost, unit or assumption.
Save comparable scenarios with the copy, link, CSV or PDF controls.
Assumptions and limitations
Training, terrain, weather, fatigue and distance specialization can make actual performance substantially different.
Real contracts, measurements, platform rules and professional standards can add inputs that this general-purpose model does not infer.
Accuracy checklist
Confirm units, time periods, fees and source figures before relying on the output.
Round the displayed answer only after the calculation; intermediate values retain full precision.
Calculation audit
| Item | What to review |
|---|---|
| Inputs | Known distance (km), Known finish time (minutes), Target distance (km), Riegel exponent |
| Equation | target time = known time × (target distance ÷ known distance)^exponent |
| Example | A 25-minute 5K predicts about 52.04 minutes for 10K at exponent 1.06. |
| Limit | Training, terrain, weather, fatigue and distance specialization can make actual performance substantially different. |
Frequently asked questions
What does this Race Time Predictor calculate?
Project an equivalent race time with the Riegel endurance equation.
Which formula does it use?
target time = known time × (target distance ÷ known distance)^exponent
Does it calculate while I type?
Yes. Valid changes update the result automatically without reloading the page.
Which inputs should I verify?
Verify every unit, period, rate and fee against the source you are modeling.
Is the result exact?
Training, terrain, weather, fatigue and distance specialization can make actual performance substantially different.
Can I save or share the result?
Yes. Copy, native sharing, WhatsApp, PDF/Print, CSV, comparison and parameterized links are available.
What to keep in mind
Training, terrain, weather, fatigue and distance specialization can make actual performance substantially different.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.