How the hydration calculator works
During exercise you lose fluid as sweat, and replacing a good share of it helps you feel and perform better. This tool estimates fluid loss from how long and how hard you work out, then suggests how much to sip during the session and how much to drink afterward to top up. These are general estimates for everyday fitness, not medical advice; needs vary a lot by person and conditions.
Sweat rate and fluid loss
Sweat rates range from roughly 400 ml an hour for easy effort to 1000 ml or more for hard work in the heat. Bigger athletes and hot, humid conditions push it higher. The most accurate way to know your own rate is to weigh yourself before and after a workout, but the levels here give a reasonable starting estimate.
Drinking during and after
For sessions under an hour, water and drinking to thirst is usually plenty. For longer or sweatier efforts, sipping steadily, roughly every fifteen to twenty minutes, helps you keep up rather than trying to catch up at the end. Afterward, a little extra beyond what you lost helps you fully rehydrate, since you keep losing some fluid through urine.
Signs and safety
Thirst, darker urine, and feeling sluggish are common signs you need more fluid. At the same time, do not force down huge volumes, since drinking far more than you lose can be dangerous. For long, intense, or hot sessions, replacing some sodium alongside fluid helps. This tool is informational only and not a substitute for advice from a doctor or sports professional.
Frequently asked questions
How much should I drink during exercise? For long or sweaty sessions, sipping roughly 100 to 250 ml every fifteen to twenty minutes is a common guide; for short workouts, drink to thirst.
How do I find my sweat rate? Weigh yourself before and after a workout; each kilogram lost is about a liter of fluid.
Do I need a sports drink? For longer or hotter efforts, replacing sodium helps; for short sessions, water is usually enough.
Related calculators: Electrolyte, Water Intake, Infused Water.