Get a personalized daily water goal based on your body weight, activity and climate — shown in ounces, cups, liters and 8-oz glasses, with a simple visual.
A water intake calculator estimates how much water you should drink each day from your body weight and activity level. A common guideline is about half an ounce to one ounce per pound of body weight, with more needed during exercise or hot weather.
Personalized daily hydration goal
Based on your body weight, activity and climate — not a generic "8 glasses" rule.
Ounces, cups, liters, 8-oz glasses and water bottles, all at once.
Runs entirely in your browser — nothing is uploaded.
The famous "8 glasses a day" rule (about 64 oz) is a handy starting point, but real hydration needs depend on your body weight, activity level, climate and overall health. A common evidence-based guideline is roughly half to one ounce of water per pound of body weight (about 30–35 ml per kg), with extra fluid to replace what you lose through exercise and heat.
This calculator estimates a baseline from your weight, then adds about 12 oz (350 ml) for every 30 minutes of exercise and adjusts for a hot or cold climate and your general activity. The U.S. National Academies suggest a total daily fluid intake of about 125 oz (3.7 L) for men and 91 oz (2.7 L) for women from all food and drink combined — roughly 80% of that comes from beverages and 20% from food.
Signs you are well hydrated include pale-yellow urine and rarely feeling thirsty. Dark urine, headaches, fatigue and dizziness can signal you need more. You do not have to hit your goal with plain water alone — milk, tea, coffee, fruit and vegetables all count toward fluid intake. Spread your drinking through the day rather than gulping it all at once, and drink a little extra when you exercise, fly, or spend time in the heat.
A note of caution: drinking too much water in a short time can dilute blood sodium (a rare condition called hyponatremia), so there is no need to vastly exceed your goal. These figures are general guidance, not medical advice — people with kidney, heart or other conditions, and pregnant or breastfeeding women, should follow their doctor's recommendations.