Enter your sex, age, height and weight to estimate how many liters of water your body holds with the Watson and Hume–Weyers formulas.
Last updated: November 8, 2026
The Watson and Hume–Weyers formulas
Between half and two thirds of your body is water. Muscle holds a lot of water and fat very little, so the share varies from person to person. With age (A, years), height (H, cm) and weight (W, kg): • Watson — men: 2.447 − 0.09156A + 0.1074H + 0.3362W; women: −2.097 + 0.1069H + 0.2466W • Hume–Weyers — men: 0.194786H + 0.296785W − 14.012934; women: 0.34454H + 0.183809W − 35.270121 • Simple rule: 60% of body weight for men, 50% for women Example: a 30-year-old man who is 175 cm (5 ft 9 in) and 70 kg (154 lb) gets 2.447 − 2.747 + 18.795 + 23.534 ≈ 42.0 L (about 11 gallons) with Watson, roughly 60% of his weight. The result is the water already in your body, not how much you should drink. For that, use the Water Intake Calculator.
Common questions about body water
About 60% in adult men, 50–55% in adult women, less in older adults and up to 75% in babies.
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Between 15 and 100.
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