Daily Water Intake Calculator
Estimate how much water to drink each day from weight and activity.
Estimates daily water needs from body weight (~35 ml per kg) plus extra for exercise. Needs also rise with heat, altitude, illness and pregnancy — drink to thirst and check urine colour. Includes water from food and drinks. Not medical advice. Runs in your browser.
Results are general estimates for information only, not medical advice — consult a qualified professional for health decisions. See how we build our calculators.
Estimate your daily water needs from your body weight (about 35 ml per kg) plus extra for exercise, shown in litres, fluid ounces and cups. Needs also rise with heat, altitude, illness and pregnancy, and water from food and other drinks counts too — so drink to thirst and check urine colour. A general guide, not medical advice.
How to use the Water Intake Calculator
- Pick metric or imperial and enter your body weight.
- Enter your typical daily exercise in minutes.
- Read your estimated daily water in litres, ounces and cups.
Frequently asked questions
How much water should I drink a day?
A common guide is about 35 ml per kg of body weight, adjusted up for exercise and hot weather. The old 'eight glasses' rule is a rough average — your needs depend on your size and activity.
Does coffee or tea count?
Yes — the fluid in tea, coffee, milk and food all contributes to hydration. The moderate caffeine in normal amounts doesn't dehydrate you.