Sweat Rate Hydration Calculator
Measure your sweat rate from weight lost during exercise and learn how much to drink per hour.
How it works
Sweat loss = (weight before − weight after) + fluid drunk; rate = sweat ÷ hours
1 kg of weight lost during exercise is about 1 litre of sweat. Adding back what you drank gives total sweat; dividing by time gives your hourly rate, a good guide for replacing fluids.
Worked example
Losing 1 kg while drinking 0.5 L over 1 hour is 1.5 L of sweat — a 1.5 L/hour rate.
Frequently asked questions
Should I replace 100% of sweat?
Aim to limit losses to under 2% of body weight. Replacing most of your hourly rate during long efforts helps performance.
Do I need electrolytes?
For efforts over an hour or heavy sweating, adding sodium helps you absorb and retain fluid.
Related calculators
General educational estimate, not medical advice. Individual needs vary — talk to a doctor or registered dietitian for personal guidance.