Heat Pace & Power Adjustment Calculator
Adjust your running pace and cycling power for temperature and humidity.
Heat and humidity make every effort harder. Pick your session, enter your pace and the conditions, and see it two ways: how much you must slow down to keep the same effort, and how much harder your usual pace becomes.
How to read this calculator
Read the result in two parts: 'Same effort' gives the pace to run so your session keeps the same feel; 'Same pace' shows the cost of forcing your usual pace (a higher heart rate and effort).
What is WBGT?
WBGT stands for Wet Bulb Globe Temperature. It is a measured heat index, not a plain air temperature: it blends three readings, a wet thermometer (humidity, sweat evaporation and wind), a black-globe thermometer (sun and radiant heat) and the air temperature, weighted outdoors 70% humidity, 20% sun, 10% air.
Why it is used here: what slows you down and raises your heart rate is the total heat load (heat, humidity and sun), not the thermometer alone. WBGT is the single validated number that sums it up, and it is the reference used by sports medicine (ACSM), athletics and the military to decide when it is safe to train. Developed for the US military in 1957 (Yaglou & Minard), it drives our estimates through Ely's (2007) marathon-weather research.
Flag thresholds: ACSM WBGT flag system (Armstrong et al., 2007), the standard for road races. The shown WBGT is an estimate from temperature, humidity and sun.
Choose your session, enter your pace, temperature and humidity, then tap Generate.