Sweat Rate Calculator
Find how fast you lose fluid during exercise from your weight before and after, what you drank and how long you trained. See your sweat rate and how much to drink to keep up.
Use this sweat rate calculator to see how much fluid you lose per hour of training and how much to drink to stay hydrated. Weigh yourself before and after a run, ride or gym session and it works out your hourly sweat loss and a drinking target. It helps runners, cyclists and anyone training in the heat plan their fluid intake.
Read the guide: How to Measure Your Sweat Rate and Drink EnoughYour session
Sweat rate
1.5 L/hr
About 1.5 L lost over the session
- Also equals
- 51 fl oz/hr
- Drink to offset most losses
- 1500 ml/hr
Aim to drink close to your sweat rate on long or hot sessions, so you finish no more than about 2% down on body weight. Don't force fluids beyond thirst on easy days. Informational only, not medical advice.
Training for endurance? Pair this with the pace calculator, target heart rate calculator and daily water intake calculator.
How it works
- 1
Weigh in before and after
Weigh yourself with little or no clothing right before and right after your session, and towel off first.
- 2
Add what you drank
Enter the fluid you drank while training and how long the session lasted. Add any urine passed too.
- 3
Read your rate
See your sweat rate per hour and a suggested drinking rate to replace most of what you lose.
Instant & 100% private — nothing is uploaded
Every calculation runs locally in your browser. The measurements, dates and details you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.
Frequently asked questions
- How do I measure my sweat rate accurately?
- Weigh yourself nearly naked before and after, towel dry both times, and note exactly what you drank and how long you went. Test in conditions like your real event, since heat, humidity and pace all change the result.
- How much should I drink during exercise?
- A common target is to drink close to your sweat rate on long or hot sessions, so you finish no more than about 2% down on body weight. Most people manage 400 to 800 ml an hour. Let thirst guide you on easier days.
- Does one kilogram of weight loss equal one litre of fluid?
- Near enough. Water weighs about one kilogram per litre, and most of the weight you lose during a workout is sweat, so we treat each kilogram (or 2.2 lb) lost as roughly one litre of fluid.
Important
These calculators give general, informational estimates and are not medical advice, diagnosis or treatment. Everyone is different — for decisions about your health, talk to a qualified clinician.
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