Water Intake Calculator
Generic "8 glasses a day" advice ignores the two things that change everything: body size and the day you're actually having. This calculator starts from ~33 ml per kilo of body weight, then adds roughly 400 ml per 30 minutes of exercise and half a liter for hot weather — the same adjustments sports-nutrition guidelines use, minus the guesswork.
The result lands in the units that matter at the fridge: liters, 500 ml bottles and 8 oz cups, so "2.9 liters" becomes "6 bottles" and an actual plan. The note line includes a realistic spread-it-through-the-day schedule, because hitting a target is about distribution, not chugging. Bookmark it — the page remembers your weight and adjusts in one tap when the workout or the heat changes tomorrow.
How to use
- Enter your weight and today's exercise minutes — the daily target updates instantly in liters.
- Toggle hot weather if it's over 30°C / 86°F, then read the same target in bottles and cups.
- Follow the distribution note across the day, and share the target with one tap on workout days.
Frequently asked questions
How much water should I drink a day?
A common baseline is 30-35 ml per kilogram of body weight — roughly 2.3 L for a 70 kg adult — before exercise and heat. This calculator uses 33 ml/kg as the baseline and then adds for today's activity and temperature, which is why the number changes day to day rather than staying fixed.
Does coffee and food count toward water intake?
Yes. All beverages count (caffeinated drinks are mildly diuretic but still net-positive), and food — especially fruit, vegetables and soup — typically supplies 20% of daily fluid. Aim most of the remaining 80% at water rather than sugary drinks.
Can I drink too much water?
Rarely, but it is real: drinking multiple liters per hour can dilute blood sodium (hyponatremia), seen mostly in endurance events. Spreading intake through the day as the schedule suggests keeps you far from that zone — thirst plus pale-yellow urine is a good practical compass.
How much extra water should I drink when exercising?
Roughly 400 ml (13 oz) per half hour of activity, more in heat or for heavy sweating — the calculator adds this automatically from your exercise minutes. For sessions beyond 90 minutes, an electrolyte drink replaces the sodium that plain water alone doesn't.