Body Water Percentage Calculator Formula

Understand the math behind the body water percentage calculator. Each variable explained with a worked example.

Use the Body Water Percentage Calculator

Formulas Used

Total Body Water

tbw_liters = 2.447 - 0.09156 * age + 0.1074 * height_cm + 0.3362 * weight_kg

Body Water Percentage

tbw_pct = (2.447 - 0.09156 * age + 0.1074 * height_cm + 0.3362 * weight_kg) / weight_kg * 100

Total Body Water

tbw_gallons = (2.447 - 0.09156 * age + 0.1074 * height_cm + 0.3362 * weight_kg) * 0.264172

Variables

VariableDescriptionDefault
weight_lbsBody Weight(lbs)180
height_inchesHeight(inches)70
ageAge(years)30
weight_kgDerived value= weight_lbs * 0.453592calculated
height_cmDerived value= height_inches * 2.54calculated

How It Works

Watson Formula for Total Body Water (Male)

TBW (L) = 2.447 - 0.09156 x Age + 0.1074 x Height(cm) + 0.3362 x Weight(kg)

The Watson formula is widely used in clinical settings to estimate total body water.

Healthy Body Water Ranges

| Category | Body Water % | |---|---| | Adult Male | 50-65% | | Adult Female | 45-60% | | Athletes | Up to 70% |

Worked Example

A 30-year-old male, 180 lbs, 70 inches.

weight_lbs = 180height_inches = 70age = 30
  1. 01Weight = 81.6 kg, Height = 177.8 cm
  2. 02TBW = 2.447 - 0.09156 x 30 + 0.1074 x 177.8 + 0.3362 x 81.6
  3. 03= 2.447 - 2.747 + 19.1 + 27.4 = 46.2 liters
  4. 04Body water % = 46.2 / 81.6 x 100 = 56.6%

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