Sweat Rate Calculator
Fluid lost per hour, and what to drink back.
Enter your values
ⓘ Live results
Results
- Sweat rate
- 40 oz per hour
- Total fluid lost
- 60 oz
- Rehydrate with (150% of loss)
- 60 oz
- Body weight lost
- 1.47%
Quick answer
Sweat rate is pre-exercise weight minus post-exercise weight, plus fluid drunk, divided by hours exercised.
Sweat rate = (weight lost + fluid drunk) ÷ hours
How to use the Sweat Rate Calculator
- 1Weigh yourself before training with minimal clothing.
- 2Track fluid drunk during the session.
- 3Weigh again afterwards and enter the numbers.
Worked example
Using the values the calculator loads with:
Inputs
- Weight before170 lb
- Weight after167.5 lb
- Fluid drunk during20 oz
- Duration1.5 hours
Results
- Sweat rate40 oz per hour
- Total fluid lost60 oz
- Rehydrate with (150% of loss)60 oz
- Body weight lost1.47%
Frequently asked questions
What loss is dangerous?
Above 2% of body weight, performance drops measurably; above 4% raises heat illness risk sharply.
Why drink 150% of loss?
Some of what you drink is excreted rather than retained, so replacing 1.5× the deficit fully restores fluid balance.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.