Mr Calcu | Reveal your body’s hydration balance and take control of your wellness journey with science-backed precision.

Discover and track your body water percentage to optimize health and boost performance—stay balanced, feel empowered, and make data-driven wellness choices.

Body Water % Estimator

Under 30

30–50

Over 50

Male

59%

Female

53%

Other/Prefer Not To Say (Avg. 54%)

Activity Level

Body Water % Estimator Guidelines

You’ve got this—accurate inputs make all the difference.

Use Accurate Inputs: Ensure recent height/weight measures and honest activity levels.
Choose the Right Formula:
- Watson: General adult use
- Boer: Overweight/obese populations
- Hume-Weyers: Clinical environments
Adjust for Special Populations:
- Pregnant individuals: Add 5–8 L to TBW
- Severe illness: Consider third-spacing or fluid retention
Applications: Used in medical dosing, hydration monitoring, and fitness analytics.

Body Water % Estimator Description

Why Total Body Water Matters

Total Body Water (TBW) is the sum of all fluid contained in your body. It influences vital systems from nutrient transport to cellular homeostasis and thermoregulation. Understanding your TBW helps optimize performance, detect imbalances, and monitor health trends.

Fluid Compartments

Intracellular Fluid (ICF): ~67% of TBW
Extracellular Fluid (ECF): ~33% of TBW, which includes:
- Interstitial fluid (~75% of ECF)
- Plasma (~25% of ECF)

Formula to Estimate TBW

TBW (liters) = Body Weight (kg) × TBW%

Example: A 70 kg person with 60% TBW has:
70 × 0.60 = 42 liters

Pro Tip: Use lean body mass–adjusted formulas for improved accuracy, especially in obese or athletic populations.

Estimation Models

Watson Formula

Male: TBW (L) = 2.447 - 0.09516 × Age + 0.1074 × Height(cm) + 0.3362 × Weight(kg)
Female: TBW (L) = -2.097 + 0.1069 × Height(cm) + 0.2466 × Weight(kg)

Other Models

Boer Formula: Better suited for overweight individuals
Hume-Weyers: Balanced for general clinical use

Real-World Case Studies

1. Endurance Athlete

Name: John, 35 years old
Height: 178 cm, Weight: 72 kg
Fitness Level: Marathon runner
TBW%: 64%, TBW: 72 × 0.64 = 46.08 L
Hydration varies by 2.5% after long training sessions

2. CHF Patient

Name: Mary, 72 years old
Height: 160 cm, Weight: 68 kg
Condition: Congestive heart failure (CHF)
TBW%: 47%, TBW: 68 × 0.47 = 31.96 L
Edema monitored via TBW trends under diuretic treatment

Edge Cases

Pregnancy: Plasma volume and amniotic fluid increase TBW by 5–8 L
Obesity: Lower TBW% due to fat's low water content (~10%)
Severe Dehydration: Plasma and interstitial compartments shrink
Muscle Wasting: Reduced TBW even if body weight remains stable
Acute Illness: Infections alter fluid compartmentalization (third-spacing)

Clinical Use

Hydrophilic drug dosing depends on TBW
Critical care: used for electrolyte planning and fluid resuscitation
Sports science: monitored alongside sodium to prevent hyponatremia

Take the first step toward smarter health—estimate your body water percentage now and unlock deeper insights into your wellness.

Example Calculation

Age	Gender	Height (cm)	Weight (kg)	Fitness Level	Estimated TBW%	TBW (L)
30	Male	180	75	Active	62%	46.5
25	Female	165	60	Sedentary	52%	31.2
50	Male	175	80	Recreational	57%	45.6
18	Female	170	58	Athlete	58%	33.6
35	Male	178	95	Obese	50%	47.5
72	Female	160	68	Chronic Illness	47%	31.96
28	Female	168	70	Pregnant	56%	39.2

Frequently Asked Questions

Muscle mass decreases with aging, reducing water storage compartments

Within ±5% for general health; clinical accuracy requires lab-based assessments (e.g., isotope dilution or bioimpedance spectroscopy).

Yes - increased blood volume and amniotic fluid elevate readings, and trimester-specific adjustment is required.

Watson is best for adults; Boer is more accurate in obese individuals. Use Hume-Weyers for broader populations.

Severe dehydration reduces plasma volume disproportionately, leading to falsely low TBW estimates unless corrected for fluid loss.

Hydrophilic medications distribute in TBW, requiring dose adjustments in fluid overload or depletion conditions.

For men, 50–65% is typical; for women, 45–60%. Athletes may exceed these ranges due to higher lean mass.