Total Body Water Calculator (Watson)
Litres of body water via the Watson equations — the standard used in dialysis dosing and hydration physiology.
Watson's regressions (from 458 adults) anchor dialysis Kt/V dosing and alcohol-pharmacokinetics (Widmark) calculations. Note the male equation loses water with age while the female one doesn't carry an age term at all — a quirk of the original dataset worth knowing if you compare across sexes.
Formula
Reference aid for healthcare professionals only. Every result must be independently verified before clinical use. Never use this tool for self-medication or to replace clinical judgement.
Litres of body water via the Watson equations — the standard used in dialysis dosing and hydration physiology. The Total Body Water Calculator (Watson) is a free, private total body water tool — every result computes instantly in your browser with no sign-up and no data upload.
About Total Body Water Calculator (Watson)
Watson's regressions (from 458 adults) anchor dialysis Kt/V dosing and alcohol-pharmacokinetics (Widmark) calculations. It applies M: 2.447 − 0.09156·age + 0.1074·H + 0.3362·W · F: −2.097 + 0.1069·H + 0.2466·W. Use the Total Body Water Calculator (Watson) to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Total Body Water Calculator (Watson)
- 1Enter your details in the Total Body Water Calculator (Watson) input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Total Body Water Calculator (Watson)?
- ✓Instant total body water result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Watson PE et al., Am J Clin Nutr 1980;33:27-39)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Total Body Water Calculator (Watson) work?+
Watson's regressions (from 458 adults) anchor dialysis Kt/V dosing and alcohol-pharmacokinetics (Widmark) calculations. The calculation uses the formula: M: 2.447 − 0.09156·age + 0.1074·H + 0.3362·W · F: −2.097 + 0.1069·H + 0.2466·W. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Total Body Water Calculator (Watson) accurate, and what is it based on?+
The method is traceable to authoritative sources: Watson PE et al., Am J Clin Nutr 1980;33:27-39. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Total Body Water Calculator (Watson) free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This is a reference aid for healthcare professionals and must be independently verified. It is not for self-diagnosis or self-medication.
What can I use the Total Body Water Calculator (Watson) for?+
It's commonly used for total body water, watson formula, tbw calculator. Litres of body water via the Watson equations — the standard used in dialysis dosing and hydration physiology.
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