Water Intake Calculator

Calculate your recommended daily water intake based on your weight and activity level. Stay properly hydrated for optimal health and performance. Free online water intake calculator.

Hot Climate?

How to Use

  1. Enter weight

    Input your current body weight in kilograms (kg).

  2. Select activity level

    Choose your typical exercise and activity level.

  3. View results

    See your recommended daily water intake in liters and number of glasses (250 ml).

What is Daily Water Intake?

Daily water intake refers to the total amount of fluid your body needs to replenish each day to maintain normal metabolism, body temperature regulation, and waste elimination. About 60% of the human body is made up of water, and roughly 2 L is lost every day through breathing, sweat, and urine.

People often recommend a flat '2 liters a day', but actual needs are proportional to body weight and vary with exercise and climate. This calculator uses 33 ml per kilogram of body weight as a baseline and adds amounts for exercise duration and hot environments to produce a personalized target.

  • Dehydration: a common cause of headaches, poor concentration, and fatigue
  • Proper hydration: helps maintain kidney function and skin and digestive health

Calculation Formula

The base recommendation is adjusted for exercise and climate.

Water (L) = weight (kg) x 0.033 + (exercise min / 30) x 0.5 + hot climate (0.5)

Example For a body weight of 70 kg, 30 minutes of exercise, and a hot climate:

  • Base: 70 x 0.033 = 2.31 L
  • Exercise: (30 / 30) x 0.5 = 0.5 L
  • Climate: +0.5 L
  • Total: about 3.3 L (rounded to one decimal place)

The number of glasses is calculated by dividing total ml by 250 ml and rounding up (e.g., 3300 / 250 -> 14 glasses).

Frequently Asked Questions

How much water should I drink per day?
This calculator uses 33 ml per kilogram of body weight as a baseline. For a 70 kg adult, that is about 2.3 liters before any additions for exercise or climate.
Should I drink more when I exercise?
Yes. To replace fluid lost through sweat, it is best to add about 0.5 L for every 30 minutes of exercise. An hour of exercise means drinking roughly 1 L more.
How much more should I drink in hot weather?
In a hot climate or extreme heat, sweating increases, so this calculator adds 0.5 L. On days with long outdoor activity or heavy sweating, you may need even more.
Is it dangerous to drink too much water?
Drinking an extreme amount of water in a short time can cause hyponatremia (water intoxication), in which blood sodium becomes diluted. However, within the normal range of drinking spread throughout the day, there is no need to worry.
Do coffee and tea count toward water intake?
Yes, the water in coffee and tea contributes partly to hydration. However, because caffeine has a diuretic effect, it is best to fill up mainly with plain water or caffeine-free drinks.
Can I get water from food too?
Yes. Water-rich foods such as watermelon, cucumber, soup, and fruit account for about 20% of total water intake. Use this calculator's result as a guide for the amount to drink as beverages.
How is the number of glasses calculated?
The total recommended amount (ml) is divided by 250 ml per glass and rounded up. For example, 2.3 L is 2300 / 250 = 9.2, so it is shown as 10 glasses.
Is it better to drink a lot at once?
Rather than drinking it all at once, it is better to drink at regular intervals throughout the day for absorption and to ease the burden on the kidneys. It is recommended to sip a little in advance before you feel thirsty.
Updated 2026 — WHO standards

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