Total Body Water Calculator (Watson Formula)
Enter age, sex, height and weight to estimate how much water your body contains.
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Total Body Water Calculator (Watson Formula) by TheCalcTools
How the Total Body Water Calculator (Watson Formula) works
Watson and colleagues fitted equations for total body water to measurements by isotope dilution. Men’s water content falls slightly with age; the women’s equation does not include age.
Adults are typically about 50 to 60% water by weight; people with more fat have a lower percentage because fat holds little water. Clinicians use the result in dialysis and fluid calculations.
The formula
Worked example
Using the default values shown in the calculator:
| Sex | Male |
|---|---|
| Age (years) | 40 |
| Height | 175 |
| Weight | 75 |
- 2.447 − 0.09516 × 40 + 0.1074 × 175 + 0.3362 × 75 = 42.7 L, 57% of body weight.
Result:
| Total body water (litres) | 42.7 |
|---|---|
| Share of body weight | 56.9% |
Frequently asked questions
How much should I drink?
Body water content is not a drinking target. Use the daily water intake calculator for that.
Sources and further reading
- Watson PE et al. (1980) Total body water volumes for adult males and females estimated from simple anthropometric measurements. Am J Clin Nutr 33:27
- Wikipedia: Body water
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This calculator gives general estimates for information and education. It is not medical advice and does not diagnose anything. Talk to a qualified health professional about your own situation. See our disclaimer.