# Total Body Water Calculator

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.

## How does total body water calculator work?

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

**For males:**

`TBW = 2.447 - 0.09156 * age + 0.1074 * height (cm) + 0.3362 * weight (kg)`

**For females:**

`TBW = -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.

## 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:
- Plasma (1/5 of extracellular fluid), which is a part of total blood volume;
- Interstitial fluid (4/5 of extracellular fluid);
- Transcellular fluid (a.k.a. "third space," normally ignored in calculations) contained inside organs, such as the gastrointestinal, cerebrospinal, peritoneal, and ocular fluids.