Calculate Fluid Requirements – That’s How it Works

Calculating your daily fluid requirements can be a useful thing because an adult consists of around 70 percent water. It is therefore particularly important to drink enough water every day.

Calculating fluid requirements – you should bear this in mind

When you calculate your fluid needs, you should keep in mind that only an average value can be calculated. How much fluid you really need depends on various factors, some of which vary daily.

  • Age: Between the ages of 15 and 51, people need the most fluids. Babies, children, and the elderly, on the other hand, have a lower fluid requirement.
  • Weight: The higher the weight, the more water the body needs.
  • Food: The values ​​given (see table) refer to the total liquid requirement of your body. So if you eat a lot of foods with a high water content (e.g. cucumbers), you need to drink less liquid.
  • Condition: Pregnant or lactating women need more fluids.
  • Activities: Athletes sweat a lot and thus excrete a large part of the liquid they take in. For this reason, the need for fluids increases in sporty people or as a result of sporting activities in general.
  • While you are physically active, it is, therefore, advisable to take in 150 to 200 milliliters of liquid every hour in addition to the daily requirement.

Calculating fluid requirements: These formulas exist

You can also calculate your daily fluid requirements using a variety of formulas. We will show you the most well-known methods for this in the following points.

  • Method 1: The DGE (German Society for Nutrition) advises: Adults should consume around 35 milliliters of liquid per kilogram of body weight per day. Seniors over 65 only 30 milliliters per kilogram.
  • Accordingly, an adult weighing 75 kilograms needs a daily amount of fluid of 2,625 milliliters. From the age of 65, this value drops to 2,250 milliliters
  • Visit the fluid requirement calculator from, here you only have to enter your weight and age. The tool does the math for you.
  • Method 2: The next method only considers your body weight. Age doesn’t matter here. Calculate 100 milliliters of liquid for the first 10 kilograms of body weight and 50 milliliters for each of the next 10 kilograms. For every additional kilogram of body weight, consume 15 milliliters of water per day.
  • For example, for a person weighing 75 kilograms, the fluid requirement can be calculated as described in the following figure.

Water intoxication: Drinking too much can be dangerous

Drinking is essential for the human body to survive. However, if you overdo it, the consequences can be serious. In order to get water intoxication, an adult (according to Austria’s public health portal) has to consume around six liters of water within a very short time. The limit is already reached at 0.4 liters for infants (one month) and at 0.9 liters for small children (one-year-old).

  • Since the body’s defense system is not yet fully functional, excessive drinking can be dangerous, especially for infants and small children.
  • In any case, infants should only drink additional liquids regularly from the 10th month of breastfeeding or baby food. For detailed information, speak to your pediatrician in advance.

Here’s how water intoxication occurs:

  • If you drink too much water, the liquid flows into the tissue and literally flushes out all the nutrients.
  • Due to nutrient deprivation, the body shows signs of dehydration. This suppresses the urge to urinate so that more minerals cannot escape.
  • Due to the simultaneous excess of water, liquid can even get into the lungs and put pressure on the brain.
  • Symptoms here are often headaches, vomiting, dizziness, and cramps.

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