Sweat Rate Calculator
Estimate exercise sweat loss and litres per hour from body-mass change, consumed fluid, urine and duration.
Your inputs
Sweat Rate Results
1 estimated L/hour
1 L estimated sweat loss
Full result table
| Mass-balance component | Signed L equivalent |
|---|---|
| Mass decrease equivalent | 0.5 |
| Consumed fluid | 0.5 |
| Urine subtracted | 0 |
An estimate using approximately 1 kg per litre and comparable weigh-ins. Other mass changes are not separately modelled. This is not a personal drinking prescription or a safe-intake limit.
Let’s work it out.
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How to use Sweat Rate Calculator
- Enter before exercise (kg), after exercise (kg), fluid consumed (ml), urine passed (ml), exercise duration (minutes).
- Calculate and compare the labelled result views. Check that every input uses the displayed unit.
- Read the worked example and limits before applying the answer.
Worked example
70 kg before, 69.5 kg after, 500 mL consumed and no urine over one hour gives about 1 L/h.
Formula, accuracy & limitations
Sweat loss L ≈ before kg − after kg + consumed L − urine L. Rate = loss ÷ exercise hours.
An estimate using approximately 1 kg per litre and comparable weigh-ins. Other mass changes are not separately modelled. This is not a personal drinking prescription or a safe-intake limit.
Calculations use your inputs. Main numeric values show up to six decimal places, percentages up to two, and chart labels up to four. Time results use hours, minutes and seconds. Very small nonzero values use scientific notation.
Read the measurement reference ↗Use comparable weigh-ins around the same exercise session
Record body mass before and after exercise, fluid consumed, urine passed and duration. Comparable dry clothing and a consistent scale matter. The model treats roughly one kilogram of mass change as one litre of fluid and does not separately estimate every other source of mass change.
Read a field estimate, not a drinking prescription
Signed mass-balance components sum to estimated sweat loss, then divide by exercise hours. Negative estimated loss triggers an input-check message rather than a negative sweat-rate label. The result does not establish a safe fluid intake, sodium replacement requirement or a diagnosis of dehydration.
Frequently asked questions
Why does urine reduce estimated sweat loss?
Urine is another measured fluid loss. Subtracting it from the total mass-balance estimate avoids counting it as sweat.
Should I drink exactly the displayed litres per hour?
The output is an exercise-session estimate, not a personal replacement prescription or safe-intake limit.
Why should I weigh myself in similar dry clothing?
Wet clothing and inconsistent scales can distort the mass difference. The estimate assumes comparable weigh-ins and treats about one kilogram of mass change as one litre.
Should I drink exactly the calculated litres per hour?
This result estimates loss during the recorded session. It is not an individual drinking prescription; conditions, tolerance and other factors still matter.
