Water Intake Calculator
Estimate how much water to drink per day from your bodyweight, with adjustments for exercise, hot weather and high caffeine or alcohol intake.
≈ 10 glasses (250 ml) · total water need incl. food ≈ 3.0 L
Educational estimate, not medical advice. Thirst and pale-straw urine remain the best day-to-day guides. For long or hot training sessions, pair water with electrolytes; some medical conditions require fluid restriction — follow your clinician’s guidance.
Hydration is a habit, not a one-off
ONDA Life builds targets like this into daily protocols and connects them to how your energy, sleep and recovery actually respond — so the habit sticks.
Download ONDA Life on the App Store →Common questions
How much water should I drink a day?
A practical baseline is about 35 ml per kg of bodyweight — roughly 2.4 litres for a 70 kg adult — then add more for exercise, heat and high caffeine or alcohol intake. Because about 20% of your water comes from food, the target from drinks is a little lower than your total water need. The “8 glasses a day” rule is a reasonable average but ignores your size and activity.
Does coffee and tea count toward hydration?
Yes. The mild diuretic effect of normal coffee or tea intake is more than offset by the water they contain, so they count toward your daily fluid. This tool adds a small extra allowance only when intake is high (several caffeinated or alcoholic drinks), since alcohol in particular is genuinely dehydrating.
How do I know if I am properly hydrated?
Urine colour is the simplest real-time gauge: pale straw means well hydrated, dark yellow means drink more. Thirst is also a reliable signal for healthy adults. Persistent dark urine, headaches or fatigue can indicate under-hydration; very frequent clear urine can mean you are overdoing it.
Can you drink too much water?
Yes, though it is uncommon. Drinking very large volumes in a short time — especially during endurance events — can dilute blood sodium (hyponatraemia), which is dangerous. Spread intake across the day, and during long or hot training sessions include electrolytes rather than water alone.
How much extra water do I need when exercising?
Roughly 350–700 ml per hour of exercise, more in heat or for heavy sweaters. This tool adds about 350 ml per 30 minutes of activity. For sessions over an hour, or anything in the heat, pair the water with sodium and other electrolytes to replace what you lose in sweat.