Running calculators
Built on 6.3 million race finishes and each race's own weather history, the same numbers every racecast.io race page uses.
Before race day
Is it too hot to race? How much will the heat slow me? →
Temperature, humidity and sun at your pace, or your race's forecast and its past race mornings.
What do the hills cost? What pace on the climbs? →
A race's mapped course, a quick flat / rolling / hilly description, or a grade-adjusted pace for one climb.
How much slower will I be at altitude? →
Your pace up there, from where you live to where you race.
Which race is faster for me? →
Two to four races priced for your time in a typical year, a bad one, or this year's forecast.