Total Body Water Calculator

Created by Małgorzata Koperska, MD
Reviewed by Bogna Szyk and Aleksandra Zając, MD
Based on research by
P E Watson, I D Watson, R D Batt Total body water volumes for adult males and females estimated from simple anthropometric measurements; The American journal of clinical nutrition; Jan 1980
Last updated: Feb 12, 2024


This total body water calculator uses your age, height, weight, and sex to estimate the volume of water in your body.

It is based on a formula developed by Dr. P.E. Watson and his team and described in 1980 in the article Total body water volumes for adult males and females estimated from simple anthropometric measurements.

If you read on, you can understand the formula and see why calculating body water by weight wouldn't be accurate.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

How does total body water calculator work?

Our calculator uses Dr. P.E. Watson's formula:

  • For males:

    TBW (l) = 2.447 - 0.09156 × age (years) + 0.1074 × height (cm) + 0.3362 × weight (kg)

  • For females:

    TBW (l) = -2.097 + 0.1069 × height (cm) + 0.2466 × weight (kg)

According to the article, these equations calculate the total body water for adults of any age, in liters (l)

Why is the total body water calculated by body weight, height, age, and sex?

You can get a rough estimate of the total body water volume on the assumption that the average human adult male consists of approximately 60% water and the average adult female is approximately 50% of water.

However, compared to several other advanced methods, the formula developed by Dr. P.E. Watson gave the best overall results.

How to interpret the calculated body water percentage?

The normal total body water volume range is 58 ± 8% for males and 48 ± 6% for females.

The body water is broken down into the following compartments:

  • Intracellular fluid (2/3 of body water) is the fluid contained within cells.

  • Extracellular fluid (1/3 of body water) is the fluid contained in areas outside of cells and consists of:

    • Plasma (1/5 of extracellular fluid), which is a part of total blood volume;

    • Interstitial fluid (4/5 of extracellular fluid); and

    • Transcellular fluid (a.k.a. "third space," normally ignored in calculations) is contained inside organs, such as the gastrointestinal, cerebrospinal, peritoneal, and ocular fluids.

You might also be interested in the blood volume calculator and our plasma volume calculator.

FAQ

How much of my body is water?

If you are a female and weigh 148 lbs, there is 50% (74 lbs) of water in your body. The usual range is 42-54% - 62-80 lbs in your case. To make the calculation more accurate, we'd need your height - to count it from P.E. Watson's formula:
Total body water = -2.097 + 0.1069 × height (cm) + 0.2466 × weight (kg)

How do I calculate total body water from weight?

There are two ways to calculate total body water from weight:

  1. To estimate the body water content knowing that the average adult male is 60% of water, and average adult female - 50%.

  2. If you know a person's age and height, you can use P.E. Watson's formula.

    For males:
    TBW = 2.447 - 0.09156 × A + 0.1074 × H + 0.3362 × W
    For females:
    TBW = -2.097 + 0.1069 × H + 0.2466 × W

Where:

  • TBW - total body water (liters);
  • A - age (years);
  • H - height (cm); and
  • W - weight (kg).

If you have found this calculator useful, you may also be interested in our pediatric blood volume calculator.

How do I increase my body water percentage?

To increase body water percentage:

  1. Drink a decent amount of water throughout the day.
  2. Drink fluids before you're thirsty.
  3. Eat plenty of fresh fruits and vegetables.
  4. More muscular people tend to have a higher water content percentage, as muscles contain more (~70%) water than fat tissue (~10%). Getting more muscular might be a way.
  5. Get a mobile app that would remind you to drink water.
  6. Add flavor to your water to make it taste better (citrus juice, artificial flavors).

How does environmental temperature affect total body water?

Total body water fluctuates throughout the day in a range of ~0.5% in hot weather. Your body will run mechanisms to keep the fluid balance even. You'll notice that you become very thirsty when in a hot environment. This will compensate for excessive sweating. You might also urinate less frequently.

Małgorzata Koperska, MD
Age
years
Height
ft
Weight
lb
Sex
Female
Body water
Total body water (volume)
l
Total body water (weight)
lb
Percentage of body weight
%
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