Water Intake Calculator
How much water you should drink per day
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A common guideline is about 33 ml of water per kg of body weight, plus roughly 350 ml for every 30 minutes of exercise. Needs rise in hot weather and with caffeine or alcohol. Thirst and pale urine are good day-to-day checks.
How to use this water calculator
Enter your body weight — you can switch between kg and lb — and the minutes of exercise you do on a typical day, then press calculate. Your daily water target appears instantly in liters and milliliters, no sign-up needed. The estimate uses about 33 ml of water per kilogram of body weight, plus roughly 350 ml for every 30 minutes of exercise.
How to read your result
The number is a daily drinking target, so spread it across the day rather than gulping it all at once. Divided into ~250 ml glasses, a 2.1 L target works out to about eight glasses: one on waking, one with each meal, and the rest in between. On training days, drink extra before, during and after your workout to cover sweat losses.
The science behind the numbers
There is no single universal water requirement — needs scale with body size, which is why weight-based formulas of roughly 30–35 ml per kg are widely used and sit close to the adequate-intake ranges published by bodies like EFSA and the U.S. National Academies. You lose water constantly through urine, breath and skin, and exercise adds sweat losses of roughly 0.5–1 L per hour. Heat, humidity and altitude push needs higher still.
Limits and practical tips
Treat the result as a starting point, not a prescription: thirst and urine color are your best day-to-day guides — pale yellow means you are on track. Needs rise in hot climates and during pregnancy or breastfeeding, while some kidney and heart conditions require a doctor-set fluid limit, and extreme overdrinking can be harmful too. For training, our sweat-rate and TDEE calculators sharpen the picture — and the CaloNote app lets you log your water alongside your meals.
Frequently Asked Questions
- How much water should I drink per day?
- A common baseline is around 30–35 ml of water per kilogram of body weight daily, plus extra for exercise. This calculator personalises that figure from your weight and activity and shows your target in both millilitres and litres.
- How does exercise change my water needs?
- Sweat during exercise increases fluid loss, so you need to drink more on active days, often an additional 350–700 ml per hour of training depending on intensity and heat. Enter your workout details and the tool adds this to your daily target.
- Does drinking water help with weight loss?
- Water can support weight loss by promoting fullness, especially before meals, and by replacing sugary drinks, but it isn't a fat burner on its own. Staying well hydrated also helps energy and performance, making it easier to stay active and eat mindfully.