Total Body Water Calculator
Estimate the total water in your body.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Water makes up the largest single component of the human body, and this calculator gives a simple estimate of your total body water from your weight and sex. You enter your body weight and select your sex, and it returns the estimated total body water in liters and as a percentage of your weight. The estimate uses well-known average fractions: total body water is roughly 60 percent of body weight for adult men and about 50 percent for adult women. This difference arises mainly because muscle tissue contains much more water than fat tissue, and body composition differs on average between sexes and individuals. Body water is vital: it fills your cells, forms the basis of blood plasma, cushions organs and joints, regulates temperature, and transports nutrients and waste. Knowing an estimate of your total body water can help you appreciate hydration needs and understand body composition metrics. This is a rough, population-average estimate, not a precise measurement; actual body water depends heavily on your specific muscle-to-fat ratio, age, and health, and it declines with age and higher body fat. More accurate assessment uses methods like bioelectrical impedance or specialized formulas that include height and age. This tool provides general information, not medical advice. Enter your weight and sex to estimate your total body water.
TBW ≈ body weight × water fraction (≈60% male, ≈50% female)
This calculator estimates total body water as a fraction of body weight, using an average of about 60 percent for men and 50 percent for women. These typical fractions reflect that muscle holds more water than fat, so people with more lean mass and, on average, men tend to have a higher water percentage than women.
Source:Human physiology
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter body weight and sex.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Total body water updates instantly as you type — no button to press.
Frequently asked questions
What percentage of the body is water?
On average, water makes up about 60 percent of body weight in adult men and around 50 percent in adult women. The exact percentage varies with body composition, since muscle holds much more water than fat, so leaner people have a higher water percentage. It also declines with age and higher body fat.
How is total body water estimated?
The simplest estimate multiplies body weight by an average water fraction, about 60 percent for men and 50 percent for women, which this calculator uses. More precise methods, such as bioelectrical impedance analysis or formulas that include height and age, give individualized results that account for your specific body composition.
Why do men and women differ in body water?
The difference comes mainly from body composition. Muscle tissue is about 75 percent water, while fat tissue is much lower. Men on average have a higher proportion of muscle and lower body fat than women, so they tend to have a higher percentage of body water. Individual variation within each sex is also large.
Why is body water important?
Body water is essential for life. It fills cells, makes up most of blood plasma, lubricates joints, cushions organs, regulates body temperature through sweat, and transports nutrients and removes waste. Maintaining proper hydration keeps these functions working, which is why adequate fluid intake matters for health, energy, and physical performance.
Is this an accurate measurement?
No, it is a rough estimate based on population-average fractions, not a precise measurement of your body. Your actual total body water depends on your individual muscle-to-fat ratio, age, and health, which this simple method cannot capture. For accurate figures, methods like bioelectrical impedance or clinical assessment are needed. This tool is for general information only.