Sweat Rate Calculator
Measure your sweat rate from a single exercise session, then predict how it changes in different heat and humidity conditions. Knowing your sweat rate is the foundation of any individualized hydration plan.
How to Use This Calculator
Weigh Yourself Before Exercise
Weigh yourself nude or in minimal, dry clothing immediately before your workout. Use a scale accurate to at least 0.1 kg (0.2 lbs).
Track Fluid Intake During Exercise
Measure how much you drink during the session. Weigh your bottles before and after, or track the volume you consume.
Weigh Yourself After Exercise
Towel off any sweat and weigh yourself in the same clothing (or nude). If you urinated during exercise, estimate the volume.
Enter Your Data Below
Plug in your numbers to calculate your sweat rate. Optionally add the environmental conditions to predict how your sweat rate would change in a different climate.
About This Tool
The core formula is standard sports science: sweat loss = (pre-exercise weight − post-exercise weight) + fluid consumed − urine volume. Dividing by exercise duration gives your hourly sweat rate. This method is used by the American College of Sports Medicine (ACSM), the Gatorade Sports Science Institute (GSSI), and sports dietitians worldwide.
The environment prediction model estimates Wet Bulb Globe Temperature (WBGT) for both your test conditions and a target environment, then scales your measured sweat rate based on research showing sweat rate increases approximately 3–4% per 1°C rise in WBGT within typical exercise ranges (Baker, 2017; Sawka et al., 2007). This is an estimate—individual variation is significant, and factors like fitness, acclimatization status, exercise intensity, and clothing all affect your actual sweat rate.
Sweat rate varies considerably between individuals and sessions. Endurance athletes typically range from 0.5–2.5 L/hr, with most falling between 0.8–1.4 L/hr. Repeat this test in different conditions and at different intensities to build a fuller picture of your sweat profile.
This calculator provides estimates for educational purposes. It does not replace individualized guidance from a sports dietitian or heat acclimation coach. For a personalized hydration and heat strategy, get in touch.