Daily Water Intake Calculator: How Much Water Per Day Free
Calculate how much water you should drink daily by weight and activity.
"8 glasses a day" doesn't fit everyone. Calculate your real hydration need in liters and glasses.
By VOV · Last updated: October 21, 2026
How it works
How it works: base of 35 ml per kilo of body weight, adjusted by activity (sedentary ×1, moderate +0.5 L, intense +1 L). A general guide for healthy adults in mild climate; heat, illness or pregnancy raise the need.
Use cases
- Calculate how many liters of water you should drink per day based on your 70-kilo body weight
- Adjust your daily hydration goal to match an intense workout routine of five days a week
- Discover how much water your body needs in summer when temperatures regularly climb above 35 degrees
Frequently asked questions
Does coffee count as water?
Partially: it hydrates despite being mildly diuretic. But don't replace water; count at most half your intake.
Can you drink too much water?
Yes, though rare: over 1 liter per hour for many hours can cause hyponatremia. Drink to thirst and with sense.
What if I train in the heat?
Add 0.5-1 L per hour of intense exercise and consider electrolyte drinks if you sweat a lot.
Do children need the same amount of water as adults?
No, children need less water than adults depending on their age and weight. The calculator is designed for adults; for kids check with their pediatrician.
Does the calculator take my body weight into account?
Yes, weight is the main input: about 35 ml per kilo per day is recommended. We also adjust for your physical activity and the climate where you live.