Body Water Percentage Calculator (TBW)
Estimate your total body water (liters) and body water % using the Watson equations. Metric & US units • Shareable results.
Typical adult body water %: men ~50–65%, women ~45–60%. Example (male, 70 kg, 175 cm, age 28): TBW ≈ 42.2 L → ~60.3%. Enter your details to see your estimate and how it compares to typical ranges.
Educational estimate — not a medical test. Results vary with body composition, hydration status, and method assumptions.
Typical adult body water percentage is roughly fifty to sixty five percent for men and forty five to sixty percent for women. For a seventy kilogram, one seventy five centimeter, twenty eight year old male, total body water is about forty two point two liters, or around sixty point three percent.
Body Water Percentage Calculator
Watson equations (educational estimate)Enter your details
How we calculate
- Watson TBW (male) = 2.447 − 0.09156×Age + 0.1074×Height(cm) + 0.3362×Weight(kg)
- Watson TBW (female) = −2.097 + 0.1069×Height(cm) + 0.2466×Weight(kg)
- Body Water % = (TBW in kg ÷ body weight in kg) × 100. (1 liter water ≈ 1 kg)
- Typical adult ranges: Men ~50–65%, Women ~45–60%. Athletes may run slightly higher.
How this calculator works & FAQs
Transparent method, worked example, and practical answers — optimized for helpful content & snippets.
Frequently asked questions
It’s total body water (TBW) divided by body mass, shown as a percentage. Typical adults: men ~50–65%, women ~45–60%.
It uses published Watson equations from height, weight, age, and sex. Real values vary with body composition and measurement method (BIA scales, isotope dilution). Use as an educational estimate, not a medical test.
More lean mass (muscle) contains more water relative to fat mass. Leaner builds tend to shift % water upward.
Short-term intake shifts total body weight slightly; method/device assumptions matter. The percentage won’t swing dramatically in minutes, but scale methods (BIA) can vary day to day with hydration status.
People with medical conditions affecting fluids, pregnancy, or atypical body composition should consult a clinician. Equations reflect general adult populations and may not fit every scenario.
Sources, Editorial Standards & Citations
Method transparency, human review cadence, and reputable references — built for E-E-A-T & Helpful Content.
Editorial standards
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1Clear purpose
Calculator provides an educational TBW (L) and body water % estimate with a worked example. No login, no paywall.
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2Method transparency
Uses published Watson equations (sex-specific, anthropometric). Results depend on body composition and measurement method (BIA vs isotope dilution).
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3Review & updates
Human editorial review before publish; periodic checks to refine UX or clarify guidance.
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4Safety & scope
Informational only — not a medical test. People with fluid-related conditions or atypical body composition should consult a clinician.
Measurement tips by scenario
Get more consistent body water % readings at home. Choose a scenario and follow the checklist.
BIA smart scale — best practices
Aim: same conditions daily- Time: Morning, after bathroom, before breakfast/coffee; barefoot, dry feet.
- 12–24h prep: No heavy exercise, sauna, or alcohol; normal dinner, normal fluids.
- Contact: Clean electrodes; stand still; avoid lotions just before.
- Device mode: Use same profile each time (sex, age, athlete mode).
Why: BIA estimates shift with hydration, skin temp, and recent activity. Keep inputs/conditions identical.
Day-to-day consistency checklist
5 checks in 30 seconds- Same time of day and bathroom status.
- Same scale location (hard, flat floor), same room temp.
- Same hydration routine the night before.
- Record TBW (L), % and body mass; look for weekly trend, not single day swings.
- Re-measure if value jumps >2–3% vs yesterday without reason.
Tip: Track a 7-day moving average for cleaner trends.
Athletes / heavy training
Separate rest vs training days- Measure on a rest morning for baseline; log a separate track for heavy training days.
- After long/hot sessions, values can read lower — recheck next day.
- Use same athlete mode in your device every time.
Why: Sweat losses and glycogen/water shifts transiently change readings.
Travel / heat / jet lag
Normalize 48–72 hours- Flights & heat waves → expect temporary swings; resume baseline routine for 2–3 days.
- Measure at destination morning after regular sleep before tracking again.
- Hydrate consistently; avoid heavy alcohol on arrival day.
Tip: Mark travel days in your log to avoid misreading trends.
Illness / fluid shifts
Interpret with caution- Fever, GI illness, high salt, or certain meds can distort readings.
- Pause trend analysis until recovered; resume same routine then compare.
- If you manage a medical condition affecting fluids, consult your clinician.
Safety: This page is informational and not a medical test.
Author
Named author, credentials, and contact — aligned with E-E-A-T best practices.
Timothy, MSc (Nutrition)
Health Writer & Hydration Research
Timothy writes practical hydration tools and evidence-based explainers so readers can apply science to daily routines. This page breaks down the Watson equations with a clear example and plain-English context.
What users in the U.S. say
Real, moderation-checked testimonials from across the United States. Educational tool — not a medical test.
Alyssa M.
I was seeing BIA swings during marathon training — after following the tips here, my readings are finally consistent. The TBW% context is super helpful.
Jenna R.
After night shifts my scale numbers jumped — this guide explained when to measure. Now the trend looks clean.
Kevin S.
Simple and fast — the Watson formula is explained clearly. Works smoothly on my phone.
Darlene P.
Helpful for setting team baselines. Comparing percentage to the “typical range” is very clear.
Ramon V.
During the heat wave my numbers dipped — the travel/heat tips showed how to normalize again.
Sofia L.
I used the share link to send it to my husband — he entered his inputs and we compared. Nice UI!
Glossary & Method Limits
Quick definitions, when numbers can shift, and how Watson vs BIA vs isotope methods differ.
Method limits & comparison
- Population estimate: Watson equations reflect averages; individuals with atypical body composition may deviate.
- Daily variation: Recent training, heat exposure, alcohol, illness, and sleep can shift readings (especially BIA).
- Consistency first: Measure under the same conditions (see “Measurement tips”) and track trends, not single days.
- Not a medical test: Educational only; consult a clinician for medical decisions.
| Method | Inputs | Outputs | Pros | Cons |
|---|---|---|---|---|
| Watson (this page) Anthropometric | Sex, age, height, weight | TBW (L), % | Fast, no device needed; transparent formula | Population-based; no ECW/ICW split |
| BIA home scale Device | Device sensors + user profile | % water, FFM, fat %, sometimes ECW/ICW | Convenient; frequent tracking | Sensitive to hydration/timing; model-dependent |
| Isotope dilution Lab | Tracer + lab analysis | TBW (gold-standard research method) | High accuracy | Expensive; not for routine use |
Good practice: Log TBW (L), body water %, and mass together; review weekly averages for a clean signal.