What this calculator does
Total body water (Watson formula) works out estimated volume of water in the body from age, height and weight. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaMen: TBW = 2.447 − 0.09156a + 0.1074h + 0.3362w; Women: TBW = −2.097 + 0.1069h + 0.2466w (a years, h cm, w kg)
The inputs explained
| Field | What to enter |
|---|---|
| Age (years) | A number, measured in years. Starts at 30. |
| Height (cm) | A number, measured in cm. Starts at 175. |
| Weight (kg) | A number, measured in kg. Starts at 75. |
| Sex | Choose from Male, Female. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with age
Every other input is held at the calculator’s starting values while age varies. Select any row to load that scenario into the calculator.