How to use this calculator
- Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
- Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
- Copy, share, save, or download your result. Saved inputs stay on this device.
How the calculation works
This differs from holding pace constant because the exponent models slower pace at longer distances. The default 1.06 is a conventional assumption, not an individual calibration. Fitness, terrain, weather, preparation and race distance affect how optimistic the estimate is. Review the units, period and assumptions before comparing scenarios. Displayed values are rounded, while the underlying calculation retains its available precision.
A worked example
A 25-minute 5 km performance with k=1.06 predicts 1,500 × 2^1.06 = 3,127.397 seconds, or about 52:07 for 10 km.
Reading your result
Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.
Frequently asked questions
What assumptions does this calculation use?
This differs from holding pace constant because the exponent models slower pace at longer distances. The default 1.06 is a conventional assumption, not an individual calibration. Fitness, terrain, weather, preparation and race distance affect how optimistic the estimate is.
Can I save or check a scenario?
The result includes the working and supporting values. Save and Restore keep inputs on this device; Copy, Download and Print export the result. Sharing a scenario explicitly includes the inputs in its link.
Sources & methodology
Vickers and Vertosick: race-time prediction research ↗
Formula review: October 24, 2026. Read our methodology.