Sweat Rate Calculator
Estimate how much fluid you lost during a workout using your pre-workout and post-workout body weight, fluid consumed, urine produced, and workout duration.
What is sweat rate?
Sweat rate estimates how much fluid you lose through sweating during exercise. It varies between people and can change with temperature, humidity, workout intensity, clothing, fitness, and acclimatization.
This calculator uses changes in body weight while accounting for fluid consumed and urine produced. The result is an individualized estimate, not a medical prescription or a required drinking rate.
How to measure your sweat rate
Weigh yourself immediately before and after training under similar conditions and while wearing as little wet clothing as practical. Record how much fluid you consume. If you urinate during the workout, include the measured amount when practical.
Repeat the measurement during different workouts and weather conditions. A cool indoor session may produce a very different result from strenuous exercise in hot weather.
How the calculation works
A higher post-workout weight does not automatically make the result invalid. Fluid consumed during training can exceed the measured change in body mass, so the calculator uses the complete formula.
Important hydration disclaimer
This tool provides an estimate for informational purposes. It does not diagnose dehydration or prescribe an exact amount to drink. Do not force excessive amounts of plain water to match a calculated number. Fluid and electrolyte needs depend on the workout, conditions, diet, health, and individual losses.