Total Body Water Calculator
Calculate your total body water volume and distribution using Watson's formula
Calculate Total Body Water
Your current body weight
Your height measurement
Age affects total body water calculation (males only)
Different formulas are used for males and females
Example Calculation
Adult Male Example
Weight: 70 kg
Height: 175 cm
Age: 30 years
Sex: Male
Calculation
TBW = 2.447 - 0.09156×30 + 0.1074×175 + 0.3362×70
TBW = 2.447 - 2.747 + 18.795 + 23.534
TBW = 42.0 L (60.0% of body weight)
ICF = 28.0 L | ECF = 14.0 L | Plasma = 2.8 L
Normal TBW Ranges
Adult Males
58 ± 8% (50-66%)
Average: ~60% of body weight
Adult Females
48 ± 6% (42-54%)
Average: ~50% of body weight
Infants
~75% of body weight
Elderly
45-50% of body weight
Decreases with age
Factors Affecting TBW
Muscle Mass
~70% water content
Fat Tissue
~10% water content
Age
Decreases with aging
Hydration Status
±0.5% daily variation
Clinical Applications
Medical Uses
- • Fluid balance assessment
- • Medication dosing calculations
- • Dialysis planning
- • Nutritional assessment
- • Body composition analysis
Health Monitoring
- • Hydration status
- • Athletic performance
- • Weight management
- • Aging effects
- • Disease monitoring
Understanding Total Body Water
What is Total Body Water?
Total body water (TBW) represents the entire volume of water contained in the human body. It's distributed across different compartments and is essential for all physiological processes, including temperature regulation, joint lubrication, and cellular metabolism.
Watson's Formula
Dr. P.E. Watson developed these equations in 1980 based on anthropometric measurements. The formulas account for sex differences in body composition and the age-related decline in body water content in males.
Clinical Significance
- •Drug dosing calculations for water-soluble medications
- •Fluid balance assessment in critical care
- •Dialysis prescription and monitoring
- •Body composition analysis
Body Water Distribution
Intracellular Fluid (ICF)
66.7% of TBW - Fluid contained within cells, responsible for cellular metabolism and maintaining cell shape.
Extracellular Fluid (ECF)
33.3% of TBW - Fluid outside cells, including:
- • Plasma (20% of ECF) - Blood component
- • Interstitial fluid (80% of ECF) - Between cells
- • Transcellular fluid - Specialized compartments