Total Body Water Calculator

Total Body Water Calculator

Water is the largest single component of the human body. This calculator estimates your total body water (TBW) in litres and as a percentage of body weight using the validated Watson formula, which uses age, sex, height and weight. TBW is typically around 50–65% of body weight — higher in men and in leaner people, and lower when body fat is higher because fat holds little water. It is used in nutrition, kidney care and fluid management as a baseline reference.

Estimate using the Watson formula. Typical total body water is roughly 50–65% of body weight (higher in men and leaner people, lower with more body fat). Hydration needs and clinical use should be confirmed with a professional.