True Pace
Strip the weather out of your run to see the pace your fitness actually holds — or predict how a goal effort will play out in the conditions you'll face.
How this is calculated
Ideal baseline. "True" conditions are ~50°F, dry, sea level, calm, clean air — where heat, moisture, thin air and wind add nothing.
Heat, humidity & sun fold into an effective temperature; the penalty grows non-linearly (a few percent in the 70s, double digits past 90°F).
Dew point over humidity. RH depends on temperature, so dew point is the truer mugginess gauge; enter either — Magnus converts.
Distance scales the heat. Thermal load accumulates: ~80% of base for a 5K, ~1.6× for a marathon.
Altitude ~1.5%/1000 ft above 3000 ft (less if acclimatized); models elevation, not hills.
Wind & air quality are modest and route-dependent; AQI is mostly a health flag.
Not modeled: hills/grade, sleep, hydration/fueling, surface. Treat every number as an estimate; let the flags override the watch.
Estimates only · not medical advice · run by feel when the flags are up