Sweat rate calculator.
Indian-heat aware sweat rate calculator. Enter pre and post-run weight, your city, temperature and humidity. Get personalised hourly hydration and sodium guidance plus WBGT category for safe running. Pairs with the Indian heat training guide.
How it works
Enter pre-run and post-run weight, fluid consumed, run duration, plus city / temperature / humidity. The calculator computes sweat rate in mL/hr, normalised mL/kg/hr, estimated sodium loss based on self-reported salt category, and a WBGT estimate using the Stull 2011 wet-bulb formula.
Why WBGT matters
Air temperature alone misleads in humid Indian conditions. WBGT (Wet Bulb Globe Temperature) accounts for humidity and heat stress. The ACSM thresholds are 18°C (Green), 23°C (Yellow), 28°C (Red), 32°C (Black). Most Indian summer mornings run Yellow to Red — plan accordingly.
Reading the verdict
The hourly hydration recommendation is 70–90% of your sweat rate. Sodium replacement is roughly half during the run, half post-run. Heavy sweaters in tropical heat may need 1000–1500 mg/hr of sodium plus 1000–1400 mL/hr of fluid. Test in training, never on race day.
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