Sweat Rate Calculator
Estimate how much fluid you lose per hour of exercise.
Quick answer: enter your details below and click Calculate Sweat Rate — your result appears instantly, right here in your browser. Nothing you enter is uploaded or stored.
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How to use
- Weigh yourself before and after exercise.
- Enter the fluid you drank and the duration.
- Click Calculate Sweat Rate.
About this tool
Weigh yourself before and after exercise, add the fluid you drank, and divide by the hours to get a sweat rate in litres per hour. Enter those four figures and the tool does the division. It is an estimate for planning drinks, not medical advice, and large losses deserve a proper hydration plan.
Frequently asked questions
Why does weight loss equal fluid loss?
Over a single session, most of the weight change is fluid, though food, clothing, and bathroom breaks add small errors.
Does heat change the rate?
Yes, a lot. Re-measure in hot conditions rather than trusting a cool-weather rate.