Total Body Water Calculator

Water makes up a large percentage of our body weight. Total body water (TBW) represents the sum of all fluid compartments in our body. Knowing your TBW can help you assess your hydration status and health. This article explains what TBW is, how to calculate it, and how to interpret the results.

What is Total Body Water?

Water is essential for life. It makes up 50-60% of our total body weight. Body water is contained both inside and outside cells in different compartments:

  • Intracellular fluid (ICF) - Fluid inside cells (about 2/3 of TBW)
  • Extracellular fluid (ECF) - Fluid outside cells (about 1/3 of TBW)

Total body water is the sum of intracellular and extracellular fluid. It depends on your age, sex, body fat percentage, and health status. Well-hydrated adult males have higher TBW (60-65% of weight) than females (50-60% of weight). Athletes also tend to have more TBW than less active people.

As we age, our body water percentages decrease. Fat tissue contains less water than muscle, so higher body fat levels also reduce TBW. Dehydration, illness, or muscle loss can quickly impact total body water.

How to calculate Total Body Water?

There are a few simple ways to estimate your total body water percentage at home:

  • Body weight method

    Multiply your weight in kg by 0.6 if male, or 0.5 if female. This gives a rough estimate of TBW.

  • Body fat method

    Subtract your body fat percentage from 100, then multiply the remainder by 0.73. This accounts for the lower water content of fat mass.

  • Watson formula

    For males: TBW = 2.447 - 0.09156 × age + 0.1074 × height + 0.3362 × weight

    For females: TBW = -2.097 + 0.1069 × height + 0.2466 × weight

    where:

    • age in years,
    • height in centimeters,
    • weight in kilograms.

Interpreting your Total Body Water results

The results of TBW calculations or body composition tests allow you to gauge your hydration status. Lower than normal TBW may indicate:

  • Dehydration - Losing over 2% of TBW through sweat, urine, diarrhea, etc. can impact performance and health.
  • Muscle loss - Since muscles are about 75% water, losing muscle also reduces TBW.
  • Obesity - Excess fat tissue lowers TBW percentage due to its low water content.

Higher than normal TBW can sometimes result from edema or water retention due to illness, hormonal changes, certain medications, etc.

Tracking TBW over time provides insights into your hydration habits, body composition, and overall health. Aim to drink enough fluids daily to maintain normal total body water percentages for your age and sex. Consult a doctor for persistent high or low values.

Based on research by

Gender
years
m
  • centimeters (cm)
  • meters (m)
  • inches (in)
  • feet (ft)
  • feet / inches
  • meters / centimeters
kg
  • grams (g)
  • kilograms (kg)
  • pounds (lb)
  • ounces (oz)
Total body water (volume)
Total body water (weight)
Body water percentage
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