Water Intake Calculator
How much water should you drink a day? Enter your weight, daily exercise and climate to get a personal target in litres, glasses and fluid ounces. Everything stays on your device.
Your daily water needs
How much water do you really need?
A practical guideline for healthy adults is about 35 ml of water per kilogram of body weight — so a 70 kg adult needs roughly 2.5 litres a day. This calculator starts from your weight, then adds about 350 ml for every 30 minutes of exercise and around 10% more in a hot or humid climate, because you lose extra fluid through sweat. Remember the total includes water from food and other drinks, not just plain glasses of water. Two easy real-world checks: you rarely feel thirsty, and your urine is pale straw-coloured rather than dark.
Exercise, heat and hydration during Ramadan
Your needs are not fixed. Long workouts, fever, pregnancy and breastfeeding all raise them, and living somewhere hot — much of Pakistan, India and the Gulf for a good part of the year — means higher baseline losses. If you are fasting in Ramadan, aim for your full daily target spread across the non-fasting hours between iftar and suhoor: drink steadily rather than all at once, and go easy on very salty or heavily caffeinated drinks that leave you thirstier. Front-loading a couple of glasses at suhoor helps you start the fast well hydrated.
Litres, glasses or ounces?
People measure water differently, so the result shows all three: litres, standard 250 ml glasses, and fluid ounces for those used to US measures. A rough hourly figure across your waking day makes the target easier to hit — a sip every so often beats gulping a litre at bedtime.
Frequently asked questions
How much water should I drink a day?
About 35 ml per kg of body weight — roughly 2.5 litres for a 70 kg adult — plus more for exercise and heat. Food and other drinks count too.
Does the 8 glasses a day rule actually work?
Eight 250 ml glasses is about 2 litres, a fair average. Basing it on your weight and activity, as this tool does, is more personal.
Should I drink more water in hot weather or during exercise?
Yes — add about 350 ml per 30 minutes of exercise and roughly 10% more in a hot or humid climate.
How should I stay hydrated while fasting in Ramadan?
Aim for your full daily target between iftar and suhoor, drinking steadily. Limit very salty and heavily caffeinated drinks, which increase thirst.
Can I drink too much water?
Rarely, but yes — a very large amount in a short time can dilute blood sodium. Spreading intake through the day avoids it for almost everyone.
Do tea, coffee and food count toward water intake?
Yes. Around a fifth of daily water comes from food, and tea and coffee still hydrate overall. The figure is total water, not just plain water.