Sweat Rate Calculator
Measure how much you sweat each hour, then learn how much to drink.
Awaiting Data
Enter your details and tap Calculate to see your results appear here.
Your result appears here.
What it measures
Sweat rate is how much fluid you lose each hour of exercise. Everyone sweats at a different pace, shaped by heat, effort, and fitness. Knowing your number helps you drink the right amount and hold performance.
Weigh yourself before and after a session, add any fluid you drank, and this tool finds your hourly loss. It then suggests how much to replace. Pair it with our Water Intake Calculator for daily needs.
How to use this calculator
- Weigh yourself before exercise.
- Note any fluid you drink during the session.
- Weigh yourself again straight after.
- Enter the numbers and duration, then Calculate.
The formula used
- weight lost
- Before weight minus after weight.
- fluid
- What you drank during the session.
- hours
- Exercise time in hours.
Understanding Your Results
Tips to Improve
- Test in conditions like your event.
- Sip steadily rather than gulping.
- Add electrolytes for long, hot sessions.
- Reweigh on hot days, since loss climbs.
Why sweat rate matters
Lose too much fluid and your pace fades, your heart works harder, and focus slips. Sweat rate puts a number on that loss, so you can drink to match it. Athletes in heat can shed well over a litre an hour, while a cool, easy session costs far less. Testing tells you which kind of day you face.
Replace fluid in step with loss, not all at once. Sip across the session, then top up afterward. On long or hot efforts, add sodium to hold the fluid you drink. Plan daily totals with our Water Intake Calculator, and gauge effort with the Heart Rate Zones tool.
Test it well
Repeat the measurement in conditions like your event for the truest figure. Weigh in light, dry clothing, and empty your bladder first. Retest as seasons change, since heat lifts sweat loss sharply. For hydration guidance, the American College of Sports Medicine offers sound advice.
Frequently Asked Questions
Aim to replace most of what you lose, spread across the session and after.
Yes. Heat, effort, and fitness all shift it, so retest now and then.
Losing over 2 percent of body weight can hurt performance. Plan ahead.
Scientific References
- Sawka, M. N., et al. (2007). Exercise and fluid replacement. Medicine & Science in Sports & Exercise, 39(2), 377–390.
- American College of Sports Medicine. (2017). Selecting and Effectively Using Hydration for Fitness.