You should aim for about
How much water should you drink a day?
Your body’s water needs depend mostly on your weight, how active you are, and your climate. A common, simple guide is around 33 ml of water per kilogram of body weight (about half an ounce per pound), then a little more for exercise and hot weather. This calculator does that maths and gives you a friendly daily target in litres, ounces and glasses — remember that food and other drinks count toward it too.
This is a general guide, not medical advice. Needs change with pregnancy, breastfeeding, illness and some medications — and it’s possible to drink too much. Listen to your thirst and check with a doctor if unsure.
Frequently Asked Questions
Is it really 8 glasses a day?
“8×8” (eight 8-oz glasses) is a rough rule of thumb, but real needs vary with your size and activity. This calculator personalizes it — for many people the answer lands near 8 glasses, for others more.
Do tea, coffee and food count?
Yes. Most drinks — even tea and coffee — count toward your fluids, and food (especially fruit and veg) provides around 20% of your water. Your target here is total fluids, not just plain water.
Can I drink too much water?
Yes, though it’s uncommon. Drinking very large amounts very quickly can dilute your blood sodium (hyponatremia). Spread your intake through the day rather than gulping it all at once.
How do I know if I’m hydrated?
A simple check: pale-yellow urine usually means you’re well hydrated, while dark yellow suggests you need more. Thirst, dry lips and fatigue are also signs to top up.