The Real Effort Calculator
Don't let the humidity lie to you. See how the weather affected your pace.
Weather Conditions
40°F75°F110°F
10%55%100%
Your Run
:min/mile
Understanding the Stress Score
The Stress Score is calculated by adding the temperature (°F) to the humidity (%). This simple formula, known as the "150 Rule" among runners, gives you a quick read on how hard your body is working to cool itself.
< 100Ideal. Chase that PR.
100-130Mild stress.
130-150Hydrate extra.
150-180Throttle back.
> 180Consider rest.
Want to learn more about running in heat and humidity? Read our guide to humidity thresholds.
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