💧 Sports Hydration Calculator
Enter your bodyweight, exercise duration, and intensity for a rough daily fluid estimate: a baseline need plus an assumed sweat loss. Drink to thirst, and never so much that you gain weight while exercising.
💧 Estimate Your Fluid Needs
What is a Sports Hydration Calculator?
It estimates how much fluid to aim for on a training day. Starting from a bodyweight-based daily baseline, it adds the fluid needed to replace sweat lost during your workout — scaled by whether the session is light, moderate, or intense — and totals it in millilitres and litres.
Even small levels of dehydration blunt endurance, strength, and focus, so planning your intake around training matters. Use this as a rough starting estimate, then adjust for heat, humidity, and your own sweat rate. It offers general fitness guidance, not a substitute for professional medical advice.
Drinking too much is dangerous too
- Drinking more than you sweat out is dangerous. Overdrinking during long exercise can dilute the sodium in your blood (exercise-associated hyponatremia), which can be fatal. If you weigh more after a session than before it, you drank too much.
- Drink to thirst, and aim to replace roughly what you lose. The total is an estimate, not a target to hit: on a cool day or at an easy pace you may lose far less.
- Learn your own sweat rate: weigh yourself before and after a session (no clothes, towel dry) and add what you drank. Each 1 kg lost is about 1 liter of fluid.
- Stop, get to shade and cool down if you feel dizziness, nausea, headache, confusion or fainting. Confusion, collapse or a very high body temperature is heat stroke: call emergency services.
- If you have a heart or kidney condition, take medication that affects fluid balance, or have been told to limit fluids, ask your doctor what is right for you.
❓ Frequently Asked Questions
How does the sports hydration calculator work?
Enter your bodyweight, how long you'll exercise, and the session intensity. It sets a daily baseline of about 35 ml of fluid per kilogram of bodyweight, then adds an assumed sweat loss based on your exercise time and intensity, giving a total in millilitres and litres. The sweat figure is an assumption: weigh yourself before and after a session to learn your own, and drink to thirst rather than to the total.
How much water should an athlete drink per day?
A common baseline is roughly 30–40 ml per kilogram of bodyweight before exercise is factored in, so a 70 kg athlete starts around 2.5 litres. Training adds to that: the harder and longer you go, the more sweat you lose and the more you need to replace. Hot, humid conditions push the requirement higher still. Replace roughly what you lose, not more: gaining weight during exercise means you drank too much.
How do I know if I'm properly hydrated?
Two everyday cues are thirst and urine colour — pale straw suggests you're well hydrated, while dark yellow signals you need to drink more. For training, weighing yourself before and after a session shows how much fluid you lost as sweat, since each kilogram of weight drop is roughly a litre to replace.
Should I only drink water during exercise?
For sessions under about an hour, water is usually enough. For longer or very intense efforts, especially in heat, you also lose electrolytes like sodium, so a sports drink or added electrolytes can help maintain performance and absorption. This tool gives general fitness guidance and isn't a substitute for professional medical advice.