Water Intake Calculator
This calculator gives a rough estimate of daily water from drinks, based on your body weight (about 30 to 35 millilitres per kilogram) plus an allowance for exercise. It returns a range in litres and cups. It is a rule-of-thumb starting point, not a medical target.
Enter your weight to estimate daily water.
A rough rule-of-thumb estimate (about 30–35 mL per kg of body weight, plus extra for exercise), not a medical target. Actual needs vary with climate, diet, pregnancy, and health conditions; food also contributes water. Heart or kidney conditions may require fluid limits — ask a clinician. Calculated in your browser.
What the Water Intake Calculator does
This calculator gives a rough daily water estimate from drinks, based on your body weight (about 30 to 35 millilitres per kilogram) plus an allowance for exercise minutes. It returns a range in litres and in 8-ounce cups.
It is a rule-of-thumb starting point, not a medical target, and it runs entirely in your browser.
How to read your result
Treat the range as a ballpark, not a quota. Thirst, urine colour, climate, and activity are better day-to-day guides than hitting an exact number.
Food contributes water too, so your total fluid needs are met by more than what you drink.
What the result is based on
The estimate multiplies body weight in kilograms by roughly 30 to 35 millilitres, a common rule of thumb, and adds about 350 millilitres per 30 minutes of exercise. US weight is converted to kilograms first; the cup figure divides millilitres by 240.
It applies no other personalization.
What it cannot tell you
- There is no single validated formula for water needs; this is an approximation, and authoritative bodies express adequate intake as total water from all sources, including food.
- Climate, pregnancy, breastfeeding, illness, and diet all change fluid needs and are not captured here.
- Some heart and kidney conditions require fluid restriction — this tool does not account for medical limits.
- It estimates water from drinks only and does not track electrolytes or overhydration risk.
Frequently asked questions
How much water should I drink a day?
There is no single correct number. This tool estimates roughly 30 to 35 millilitres per kilogram of body weight plus extra for exercise, but authoritative guidance frames adequate intake as total water from all sources, including food.
Is the calculator a medical target?
No. It is a rule-of-thumb estimate. Thirst and urine colour are practical day-to-day guides, and some heart or kidney conditions require fluid limits set by a clinician.
Does food count toward hydration?
Yes. A meaningful share of daily water comes from food, so your drinking target does not need to cover all of it.
This tool is for education and planning. It does not diagnose, prescribe, or replace advice from a licensed clinician. Bring your result to a provider to decide what is right for you.