Running, cycling and training
Sweat Rate Calculator
Measure fluid loss from a representative workout and convert it into litres per hour. Save several results across different conditions rather than treating one test as permanent.
Measured workout estimate
Calculate your sweat rate
Use weights from the same scale, with similar dry clothing, immediately before and after a representative session.
Example result — enter your measurements
Higher observed rate: this label only compares the observed rate with broad planning bands. Repeat the test in different weather and intensities to build your own range. The measured rate describes loss during this session; it is not automatically the amount you should force yourself to drink each hour.
Describe this sessionStored only if you save
Weights and drink amounts are used for the calculation but are not stored in the journal. You can remove any saved session below.
Safety: do not deliberately dehydrate, overdrink, or use this tool to “make weight.” If you have experienced heat illness, hyponatraemia, fainting, or unusually high losses, seek advice from an appropriately qualified clinician or sports dietitian.
Private comparison journal
Compare measured sessions
See how observed results differed with activity, intensity and conditions. This is a comparison of tests, not a diagnosis or permanent personal rate.
Save the result above after a representative workout. Two or more tests make the condition comparison more useful.
Why personal measurements beat a generic hourly number
Sweat rate varies greatly between people and within the same person. Body size, intensity, temperature, humidity, clothing, equipment and heat acclimatisation can all change the result. A cool recovery run and a hard summer ride should not share one assumed loss rate.
The National Athletic Trainers’ Association recommends quantifying sweat rate in realistic environments and using the result as part of an individual plan that avoids both excessive dehydration and overdrinking. This calculator follows its published equation.
How to run a useful test
- Use the same reliable scale immediately before and after exercise.
- Wear minimal, similar clothing and towel away excess sweat before the second measurement.
- Record every drink consumed during the session.
- Record urine passed when practical.
- Repeat the test in different conditions and compare the range.
Sweat-rate questions
What is a normal sweat rate?
There is a wide individual range. The useful comparison is your own repeated measurements in similar activities and conditions, not a single population average.
How do I calculate my sweat rate?
Subtract post-exercise weight from pre-exercise weight, add fluid consumed, subtract urine passed, then divide the estimated litres lost by exercise hours.
Does sweat rate change in hot weather?
Yes. Temperature, humidity, sun, clothing, intensity and acclimatisation can all change sweat loss.
How often should I measure my sweat rate?
Repeat representative tests when activity, intensity, season, clothing or environment changes. Keep several results rather than treating one test as permanent.
Do fitter people sweat more?
Training and acclimatisation can change sweating, but fitness alone cannot predict an individual rate. Measure under realistic conditions.