Sumyard

Race time predictor

Compare race distances with a configurable Riegel power-law model.

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A power-law comparison is not a personal performance guarantee. Fitness, training, course, weather and distance-specific endurance affect results.

Your inputs

Updates as you type

modeled target race time

0:52:07

Distance multiplier
2×
Model exponent
1.06

Riegel power-law model with your entered exponent.

Calculations happen in your browser. Saving is optional.

How to use this tool

Enter a recent race time and distance, then the target distance.

Choose the Riegel exponent and compare the projected time cautiously. Course, weather, training and distance-specific endurance can change performance.

Predicted time = known time × (target distance / known distance)^exponent

Worked example

0:52:07 · modeled target race time

Fixed example using the settings below. Monetary examples use USD; dates and times use their stated reference values. This example stays unchanged when you edit your calculation.

Example inputs
  • Recent race time (hours:minutes:seconds): 0:25:00
  • Recent race distance (km): 5
  • Target race distance (km): 10
  • Riegel exponent: 1.06

Method illustration: A 25-minute 5K projects to about 52:07 for 10K with exponent 1.06.

Assumptions and limits

  • A power-law comparison is not a personal performance guarantee. Fitness, training, course, weather and distance-specific endurance affect results.
  • Use a recent maximal race on a comparable course. Extrapolating far beyond the known distance is especially uncertain.

Check or report a result

Check the units, selected calculation and assumptions first. Compare the fixed example above with your inputs to identify what changed.

Report a calculation issue with the page address, hypothetical inputs, result displayed and result expected. Do not include passwords, bank details or other private information.