Personal hydration planner
Turn a sweat-rate test into a planning range for a similar session, without a one-size-fits-all drinking rule.
Sweat rate test analyzer
Use a simple before-and-after field test to estimate how much fluid you lost in that session.
Sweat rate test analyzer
Example valuesUse a simple before-and-after field test to estimate how much fluid you lost in that session.
No account needed. Calculations happen in your browser; your entries are not saved or sent to Century.
Example · Estimated sweat rate
1.00L/h
A one-session estimate; conditions and wet clothing can change it.
- Estimated sweat loss
- 1.00 L
- Body-mass change
- 0.71%
How it’s calculated
Estimated sweat loss in liters = pre-exercise mass (kg) − post-exercise mass (kg) + fluid consumed (L) − urine passed (L), treating 1 kg of acute mass change as roughly 1 L of fluid. Divide by exercise hours for sweat rate. Use dry clothing, the same scale and similar measurement conditions. Fuel, respiratory water and other losses add uncertainty; the estimate does not measure sweat sodium.
Reference: ACSM: Exercise and fluid replacement position stand
For general wellness information. This tool does not diagnose health conditions or replace medical advice.
Related tools
All tools
Sweat rate test analyzer: use your own data
What to enter
Use a simple before-and-after field test to estimate how much fluid you lost in that session.
Drinking offsets part of the body-mass drop. Adding it back estimates fluid lost during the session; subtracting urine avoids counting fluid that left through urination as sweat.
Read the result in context
Estimated sweat loss is 0.5 + 0.5 = 1.0 L, giving a session sweat rate of 1.0 L/h.
Sweat rate varies with temperature, humidity, clothing and intensity. Repeat under conditions like the activity you want to plan.
Where this estimate stops
Body-mass change and fluid intake cannot determine sweat sodium concentration.
Put your training and recovery data together in Century.
Frequently asked questions
What do I need for a sweat-rate test?
Record body mass before and after a session, fluid consumed, urine passed if any, and exercise duration. Weigh in similar dry clothing on the same scale.
Why add the water I drank?
Drinking offsets part of the body-mass drop. Adding it back estimates fluid lost during the session; subtracting urine avoids counting fluid that left through urination as sweat.
Can I use one result in any weather?
No. Sweat rate varies with temperature, humidity, clothing and intensity. Repeat under conditions like the activity you want to plan.
Does this tell me how much sodium to take?
No. Body-mass change and fluid intake cannot determine sweat sodium concentration.