Lifestyle
Food & Nutrition
FitnessHow much water you should drink per day, based on your body and lifestyle.
This tool is for general information only and is not medical advice. Talk to a healthcare professional about results that concern you.
How Much Water Should You Drink a Day?
The old “8 glasses a day” rule is not wrong, but it ignores the two things that change your needs most: your body size and how much you sweat. A 55 kg office worker and a 95 kg construction worker do not need the same amount of water. This calculator starts from about 33 ml per kilogram of body weight, then adds extra for exercise and hot weather.
For reference, the U.S. National Academies suggest a total fluid intake of about 2.7 liters a day for women and 3.7 liters for men. Those totals include roughly 20 percent that arrives through food, especially fruit, vegetables, and soups, so your drinking target is lower than the headline number.
Signs You Are Not Drinking Enough
- Dark yellow urine (pale straw is the goal)
- Headaches in the afternoon
- Feeling tired or foggy for no clear reason
- Dry mouth and lips
- Feeling hungry shortly after eating (thirst mimics hunger)
Spread your intake through the day rather than drinking large amounts at once. A glass when you wake up, one with each meal, and one around exercise covers most of your target without any tracking. Hydration also plays a supporting role in weight management; our calorie calculator covers the other side of that equation.
Frequently Asked Questions
Do coffee and tea count toward my water intake?
Yes. The diuretic effect of caffeine at normal doses is too small to cancel out the fluid. Coffee, tea, milk, and even the water in food all count toward daily hydration.
Can you drink too much water?
Yes, though it is rare. Drinking many liters in a short period can dilute blood sodium (hyponatremia), which is dangerous. Spread intake across the day and let thirst guide you during long exercise.
Does drinking water help with weight loss?
Modestly. Water before meals increases fullness, and replacing sugary drinks with water removes calories directly. It supports a diet; it does not replace one.
How much water should I drink when exercising?
A practical rule is 300 to 500 ml per half hour of sweaty exercise, which is what this calculator adds. For sessions over an hour in heat, an electrolyte drink becomes worth considering.
Sources
- Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate · National Academies
- Read "Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate" at NAP.edu · National Academies
- Water in diet: MedlinePlus Medical Encyclopedia · MedlinePlus
- Water, Hydration and Health · PubMed Central (PMC)
This calculator is for general information only and is not a substitute for professional medical advice.