Body Water Percentage Calculator (Watson formula)
Total body water in litres and as % of body mass, via the Watson (1980) anthropometric formula. Illustrative — consult a professional for clinical use.
Result
- Sexmale
- Age30 yr
- Weight75.0 kg (165.3 lb)
- Height175.0 cm (68.9 in)
- Total body water (TBW)43.71 L
- Body water %58.28%
- Intracellular fluid (~⅔)29.14 L
- Extracellular fluid (~⅓)14.57 L
- Reference band (adult male)55-65%
- VerdictWithin typical adult male range (55-65%).
- DisclaimerIllustrative anthropometric estimate. NOT a clinical diagnostic. Consult a healthcare professional for medical questions.
Step-by-step
- Male: TBW = 2.447 − 0.09156·30 + 0.1074·175.0 + 0.3362·75.0 = 43.710 L.
- Body water % = TBW / weight × 100 = 43.71 / 75.0 × 100 = 58.28%.
- Intracellular ≈ ⅔ TBW = 29.14 L; extracellular ≈ ⅓ TBW = 14.57 L.
How to use this calculator
- Enter biological sex (the formula has two sex-specific regressions).
- Age in years.
- Weight in kilograms (or lb ÷ 2.2046).
- Height in centimetres (or in × 2.54).
- Compare your % to the reference band shown for your sex.
About this calculator
Total body water (TBW) is the amount of water in your body — typically 50-65% of body mass in adults, lower in those with higher body fat (fat tissue holds less water than lean tissue). The Watson formula (1980) estimates TBW from sex, age, height, and weight using a regression developed from deuterium-oxide-dilution studies in healthy adults. It is the most widely cited anthropometric TBW estimator in clinical pharmacology (used to dose hydrophilic drugs and to plan dialysis) and in nutrition research. The two sex-specific equations: TBW_male = 2.447 − 0.09156·age + 0.1074·height_cm + 0.3362·weight_kg; TBW_female = −2.097 + 0.1069·height_cm + 0.2466·weight_kg. About two-thirds of TBW is intracellular fluid (inside cells); one-third is extracellular (blood plasma + interstitial fluid). Healthy adult ranges: men 55-65% body water, women 45-60% — women average lower because of higher essential body-fat percentage. Lean athletes can run higher; people with obesity tend to run lower. This calculator is illustrative; it cannot diagnose dehydration or fluid-balance disorders.