Sweat Rate Calculator
How much fluid you lose per hour of exercise, from your weight before and after, what you drank and the duration.
Results
Sweat rate
1.30
L/h
Total sweat lost
1.30
L
Body mass lost
1.14
%
Drinking that would match it, every 15 minutes
325
mL
What this tool does
Weighing yourself before and after a session is the standard field method sports scientists use: one kilogram lost is about one litre of sweat, plus whatever you drank in between. Sweat rates vary enormously between people and conditions — from under half a litre to over two litres an hour — which is why a personal measurement beats a generic rule. Losing more than about 2 % of body weight is commonly linked with poorer endurance performance; drinking far more than you sweat is risky too. Weigh with minimal, dry clothing.
Formula
sweat (L) = (weight before − weight after) + fluid drunk − urine · rate = sweat ÷ hours
Variables
| Symbol | Meaning | Unit |
|---|---|---|
pre | Body weight before exercise | kg |
po | Body weight after exercise | kg |
fl | Fluid drunk during exercise | L |
ur | Urine passed during exercise | L |
du | Exercise duration | min |
SR | Sweat rate | L/h |
SL | Total sweat lost | L |
BL | Body mass lost | % |
DQ | Drinking that would match it, every 15 minutes | mL |
Worked example
- Body weight before exercise70 kg
- Body weight after exercise69.2 kg
- Fluid drunk during exercise0.5 L
- Urine passed during exercise0 L
- Exercise duration60 min
- Sweat rate1.30 L/h
- Total sweat lost1.30 L
- Body mass lost1.14 %
- Drinking that would match it, every 15 minutes325 mL
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.