Daily Water Intake Calculator

How much water should you drink each day?

There is no glass count that fits everyone. Body size, water in food, weather and sweating all affect fluid needs. This tool uses a practical adult rule of 33 ml/kg to estimate a starting amount from drinks. The rule is not a measurement of individual requirements or an average of several equations.

Example: 70 kg × 33 ml = 2,310 ml, or 2.31 litres. That is 11.55 glasses at 200 ml each, or 9.24 glasses at 250 ml each.

Do not treat the result as a compulsory drinking target. Selecting pregnancy, breastfeeding or a prescribed fluid restriction withholds an automatic amount. The tool also withholds a number above 120 kg because extending a fixed ml/kg rule can produce an excessively large target. This is a tool limitation, not a medical weight threshold.

Drinking water and total water are different

Total water intake includes water in drinks and food. Counting only plain water leaves out contributions from soup, milk, yoghurt, fruit and vegetables. EFSA’s adult reference values of around 2 litres for women and 2.5 litres for men concern total water; they do not mean everyone must drink that much extra plain water.

The 33 ml/kg result here is a practical rule for drinks. Do not add it to a total-water reference as though they were separate requirements. The guide to water and daily intake discusses how hydration fits into everyday life.

Water by weight: litres and glasses

A glass is not a standardized volume. Measuring your usual glass once makes the count more useful. You can select 200, 240, 250 or 300 ml: the fluid volume stays the same while the glass count changes. The result uses one decimal place, so it may show a small rounding difference from the two-decimal examples above.

Exercise, heat and additional fluid

If you enter today’s exercise duration, the tool adds an illustrative 400 ml per hour. A 60-minute session adds 400 ml once; there is no second weekly activity multiplier. This does not measure your sweat rate. Heat, prolonged training and heavy sweating can change both fluid and electrolyte needs.

Do not try to meet a target by forcing large amounts during a workout. Unusual conditions or endurance events call for a more individual plan. The target heart rate guide adds context about exercise intensity.

Eight drinking breaks are not eight glasses

The result includes an example dividing the amount into eight portions. At 2,310 ml, each portion is about 289 ml, which is not the same as one 200 ml glass. You could spread drinks across waking, meals and familiar breaks in your day. It is a planning example, not a requirement to finish a fixed portion whenever a clock says so.

Urine colour, excessive intake and special circumstances

Urine colour can be a daily clue, but vitamins, medicines and foods can also change it. Selecting a colour on a screen is not a hydration measurement. More fluid is not always better: excessive rapid intake can cause problems, and there is no universal safe five-litre limit here.

Adult estimates are not used for children. The Holliday–Segar approach used in hospital fluid management is not a prescription for how much a child should drink at home. Explore nutrition during lactation in the breastfeeding calorie guide, or read whether drinking water helps weight loss for that separate question.