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Use this free Total Body Water (TBW) Calculator to accurately estimate the total volume of water in your body — measured in both liters and as a percentage of total body weight — based on your age, gender, height, and weight using the clinically validated Watson Formula for Total Body Water, the most widely referenced TBW estimation equation in medical and sports science research. Total body water typically constitutes 45–60% of body weight in adult women and 50–65% of body weight in adult men, distributed across two primary fluid compartments: Intracellular Fluid (ICF) — the water held within cells, accounting for approximately 60% of total body water — and Extracellular Fluid (ECF) — comprising blood plasma, interstitial fluid, and lymphatic fluid. Maintaining optimal body water percentage is essential for cellular hydration, cardiovascular circulation, electrolyte balance, thermoregulation (body temperature control), kidney function and toxin elimination, joint lubrication, and peak cognitive and athletic performance. Deviations from your healthy TBW range may indicate dehydration, overhydration (hyponatremia), edema, or underlying metabolic and renal health conditions. This body water percentage calculator is used by sports scientists, clinical dietitians, nephrologists, and fitness professionals to assess hydration status, monitor fluid retention, and optimize daily water intake recommendations for better health, recovery, and physical performance.
Total Body Water (TBW) represents the total amount of water contained in the human body. Water is the most abundant substance in the body and plays a crucial role in maintaining essential biological functions such astemperature regulation, nutrient transport, metabolism, and cellular function.
A Total Body Water calculator estimates how much water is contained in your body based on variables such asbody weight, height, age, and gender. These estimates help understand hydration levels and body composition.
The human body stores water in two main compartments:intracellular fluid and extracellular fluid. These compartments help regulate electrolyte balance and maintain proper organ function.
Maintaining healthy hydration levels supportscirculation, oxygen delivery, digestion, and metabolic efficiency.
Most Total Body Water calculators estimate TBW using theWatson Formula, a medical equation developed from clinical studies measuring hydration levels in adults.
The Watson formula estimates body water using a combination ofbody weight, height, age, and gender.
Watson Formula for Men:
Watson Formula for Women:
These equations estimate how much fluid is present in the body by accounting for differences in body composition between men and women.
Although laboratory techniques such asbioelectrical impedance analysis (BIA) orisotope dilution testing provide more precise results, the Watson equation remains one of the most widely used methods for estimating Total Body Water.
The percentage of water in the human body varies depending onage, gender, and body composition. Muscle tissue contains more water than fat tissue, which explains why individuals with higher muscle mass often have greater TBW percentages.
| Group | Typical Body Water Percentage |
|---|---|
| Adult Males | 55% – 65% |
| Adult Females | 45% – 60% |
| Infants | 70% – 75% |
| Children | 60% – 70% |
| Elderly Adults | 50% – 55% |
Because body fat contains less water than muscle, individuals with higher fat percentages often have lower overall Total Body Water.
Water plays a fundamental role in nearly every biological process in the human body. Maintaining adequate hydration helps ensure that cells, organs, and tissues function efficiently.
Key functions of body water include:
Even mild dehydration can affectenergy levels, concentration, and physical performance. Monitoring hydration levels using aTotal Body Water calculator can help individuals understand their body composition more effectively.
Several biological and lifestyle factors affect the amount of water present in the body.
Tracking hydration levels can supportathletic performance, metabolic health, and overall wellbeing.
Total body water represents the total amount of fluid contained in the human body, including water inside cells, between cells, and within the bloodstream.
On average, about 50–65% of adult body weight consists of water, although the percentage varies depending on age, gender, and body composition.
Body water is essential for maintaining body temperature, transporting nutrients, regulating metabolism, and supporting cellular functions.
Total body water can be estimated using formulas such as the Watson formula, which considers factors like age, height, weight, and gender.
Most TBW calculators use the Watson equation or similar medical formulas to estimate body water based on body measurements.
Water makes up roughly 60% of the human body in adults, though the percentage may range from 45% to 75% depending on age and body composition.
Yes. Muscle tissue contains more water than fat tissue, so individuals with higher muscle mass generally have higher body water percentages.
Yes. People with higher body fat typically have a lower percentage of total body water because fat tissue contains less water.
Intracellular water is the fluid inside cells, while extracellular water refers to fluid outside cells, including blood plasma and interstitial fluid.
Daily hydration needs vary by body size, climate, and activity level, but many guidelines recommend around 2–3 liters of water per day.
Yes. Dehydration temporarily reduces the body's total water content and may affect energy levels, circulation, and metabolic functions.
Dehydration can occur due to insufficient water intake, excessive sweating, illness, intense exercise, or hot weather conditions.
Hydration levels can be estimated through body water calculators, bioelectrical impedance devices, or laboratory testing.
No. Men generally have higher body water percentages than women due to higher lean muscle mass.
Yes. Infants have higher body water percentages, while older adults typically have lower water content.
Low body water levels can lead to dehydration, fatigue, dizziness, and impaired physical and cognitive performance.
Excessive water intake can lead to a rare condition called water intoxication or hyponatremia.
Yes. Hydration levels fluctuate throughout the day depending on diet, exercise, and fluid intake.
Yes. Water plays a critical role in metabolic reactions and nutrient transport throughout the body.
Athletes often have higher body water percentages due to increased muscle mass and lower body fat.
No. TBW calculators provide estimates and should not replace professional medical assessments.
The Watson formula estimates total body water using body weight, height, age, and gender to approximate hydration levels.
The calculator provides a reliable estimate based on established formulas but may not match laboratory measurements exactly.
Yes. This total body water calculator is completely free and works instantly in your browser.
No. All calculations are performed locally in your browser and no personal data is stored.