Estimate body water percentage from weight, height, age and sex using Watson formula — see total body water liters and percent.
Estimate body water percentage from weight, height, age and sex using Watson formula — see total body water liters and percent.
Enter values above and click Calculate — results will appear here with the formula explained.
Total body water is predicted from weight, height, age and sex through the Watson equations derived from isotope dilution studies: male total water equals 2.447 minus 0.09516 times age plus 0.1074 times height plus 0.3362 times weight, with a parallel female formula. Dividing predicted water in liters by weight and multiplying by 100 yields percent — typically 50–65% in healthy adults, trending lower with higher adiposity and with age as muscle mass declines, and generally a few points lower in women due to average fat fraction.
Watson is an anthropometric estimate, not bioimpedance or isotope measurement; dehydration, edema, diuretic use and altered body composition all degrade its accuracy for individuals. Use the percent to contextualize hydration targets and weight changes, not to diagnose fluid status — clinical fluid assessment relies on examination and labs, not equations.
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Total body water is predicted from weight, height, age and sex through the Watson equations derived from isotope dilution studies: male total water equals 2.447 minus 0.09516 times age plus 0.1074 times height plus 0.3362 times weight, with a parallel female formula. Dividing predicted water in liters by weight and multiplying by 100 yields percent — typically 50–65% in healthy adults, trending lower with higher adiposity and with age as muscle mass declines, and generally a few points lower in women due to average fat fraction. Formula: Watson: Male TBW =2.447 -0.09516*age +0.1074*height +0.3362*weight; Female = -2.097 +0.1069*height +0.2466*weight
Body Water Percentage Calculator: Estimate body water percentage from weight, height, age and sex using Watson formula — see total body water liters and percent. Formula: Watson: Male TBW =2. Example: At 70kg, 175cm, 30 male: TBW about 42.
Estimate body water percentage from weight, height, age and sex using Watson formula — see total body water liters and percent. Formula: Watson: Male TBW =2.447 -0.09516*age +0.1074*height +0.3362*weight; Female = -2.097 +0.1069*height +0.2466*weight
| Field | What to enter |
|---|---|
| Weight (kg) | e.g. 70 |
| Height (cm) | e.g. 175 |
| Age | e.g. 30 |
| Sex | Enter a value |
All fields use the exact formulas shown below — results include step-by-step breakdowns you can verify by hand.
Total body water is predicted from weight, height, age and sex through the Watson equations derived from isotope dilution studies: male total water equals 2.447 minus 0.09516 times age plus 0.1074 times height plus 0.3362 times weight, with a parallel female formula. Dividing predicted water in liters by weight and multiplying by 100 yields percent — typically 50–65% in healthy adults, trending lower with higher adiposity and with age as muscle mass declines, and generally a few points lower in women due to average fat fraction.
Watson is an anthropometric estimate, not bioimpedance or isotope measurement; dehydration, edema, diuretic use and altered body composition all degrade its accuracy for individuals. Use the percent to contextualize hydration targets and weight changes, not to diagnose fluid status — clinical fluid assessment relies on examination and labs, not equations.
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At 70kg, 175cm, 30 male: TBW about 42.1L, ~60.1% of weight.
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