Daily Water Intake Calculator

HealthLast updated: August 17, 2026

About 60% of the human body is water, and fluid balance is critical for regulating body temperature, lubricating joints, digestion, and kidney health. Daily water needs are not the same for everyone: the requirement grows with body weight, and the fluid lost as sweat during exercise has to be added on top.

This calculator uses the widely applied rule of 35 ml per kilogram of body weight for your baseline need and adds roughly 350 ml for every 30 minutes of exercise. The result is shown both in liters and in standard 200 ml glasses, which makes it easy to track through the day.

kg
min
Leave it at 0 if you do not exercise. About 350 ml is added for every 30 minutes.

Water Intake Reference Values

Daily water intake is not a fixed number of liters but a range that depends on body weight and activity. This calculator uses the upper reference of 35 ml per kilogram; every value that feeds into the result is listed below.

Daily water per kilogram
30 – 35 ml
The common reference range for healthy adults; this calculator uses the upper end of the range (35 ml/kg)
Exercise add-on
~350 ml / 30 min
Added for every 30 minutes of exercise to replace the fluid lost through sweat
Increase in hot weather
10 – 20%
High temperature, humidity, and altitude all increase sweating, so the daily requirement should be raised
Glass equivalent
200 ml
The number of glasses in the result is computed by taking a standard glass of water as 200 ml

General nutrition references that remain in force for healthy adultsKaynak: Republic of Turkey Ministry of Health — Turkey Dietary Guidelines, and the EFSA reference values for water intake

Formula

Baseline need (ml) = Weight (kg) × 35
Exercise add-on (ml) = (Exercise time / 30 min) × 350
Daily need (L) = (Baseline + Add-on) / 1000
Number of glasses = Total ml / 200

The 35 ml/kg figure is a practical rule of thumb widely used for healthy adults. Needs rise in hot weather, during a fever, and in pregnancy and breastfeeding; drinks such as tea and coffee and water-rich foods also count toward total fluid intake.

How to Calculate

  1. Enter your body weight in kilograms.
  2. Enter the total time you exercise during the day in minutes; leave it at 0 if you do not exercise.
  3. Read your daily water requirement in liters and in glasses.
  4. Spread the total across the day: starting with 1-2 glasses in the morning and drinking with every meal and during exercise breaks makes it easier to keep up.

Worked Examples

A 70 kg adult who does not exercise

For 70 kg the baseline need is 70 × 35 = 2,450 ml; with no exercise the total is 2.45 liters, which is about 12 glasses of water.

Daily water requirement: 2.45 liters · Equivalent in glasses: ≈ 12 glasses · Baseline need (35 ml × weight): 2,450 ml

An 80 kg adult training one hour a day

For 80 kg the baseline need is 2,800 ml, and 60 minutes of exercise adds 700 ml. The total comes to 3.50 liters, or roughly 18 glasses.

Daily water requirement: 3.50 liters · Equivalent in glasses: ≈ 18 glasses · Baseline need (35 ml × weight): 2,800 ml

A 55 kg adult taking a half-hour walk

For 55 kg the baseline need is 1,925 ml and the 30-minute walk adds 350 ml; the recommended total is 2.28 liters, about 11 glasses.

Daily water requirement: 2.28 liters · Equivalent in glasses: ≈ 11 glasses · Baseline need (35 ml × weight): 1,925 ml

Frequently Asked Questions

Is the eight-glasses-a-day rule correct?
The eight-glass rule (about 2 liters) is a handy average, but it does not fit everyone. A 50 kg person and a 100 kg person cannot need the same amount; working from 30-35 ml per kilogram gives a personalized and far more accurate estimate.
Do tea, coffee, and other drinks count as water?
Partly, yes. Current research shows that caffeinated drinks also make a net contribution to daily fluid intake; their mild diuretic effect does not cancel out the fluid they provide. Even so, sugary drinks should not replace water because of their calorie load, and most of the requirement should come from plain water.
Can drinking too much water be harmful?
Yes, though it is rare. Drinking a very large amount in a short time can dilute blood sodium and cause hyponatremia, which presents with headache, nausea, and in severe cases confusion. Spreading your intake across the day and staying under 1 liter per hour is a safe approach.
How do I know whether I am drinking enough?
The most practical indicator is urine color: pale straw yellow points to adequate fluid intake, while a dark yellow to orange shade signals a shortfall. Thirst, a dry mouth, and fatigue during the day can also be early signs of mild dehydration.
How much does the requirement rise in hot weather or during sport?
It rises noticeably, depending on how fast you sweat. Losing 0.5 to 1 liter of sweat per hour is common during intense exercise; this calculator covers that approximately by adding 350 ml for every 30 minutes. On hot, humid days it is sensible to add a few hundred milliliters to the total even without exercise.
Does water intake change during pregnancy and breastfeeding?
Yes. About 300 ml of extra fluid per day is recommended in pregnancy, and up to 700 ml while breastfeeding because of milk production. In these periods, treat the calculated value as a floor and increase it according to your doctor's advice.