Enter your body weight and basic details to estimate your total body water (TBW) amount and volume.
Disclaimer: This calculator provides an educational estimate and is not medical advice or a diagnostic tool. Do not use it to guide IV fluids, diuretics, or treatment decisions. Talk with a clinician if you are pregnant, under 18, older, or have kidney, heart, or liver disease, edema, or fluid-balance concerns; seek urgent care for severe dehydration symptoms (confusion, fainting, inability to keep fluids down).
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Total Body Water Formula
This calculator estimates total body water (TBW) using the Watson formula (commonly used as an adult estimate). TBW varies by sex, age, and body composition, so any formula-based result is an estimate rather than an exact measurement.
TBW_{male}(L)=2.447-0.09516\cdot Age+0.1074\cdot Height(cm)+0.3362\cdot Weight(kg)TBW_{female}(L)=-2.097+0.1069\cdot Height(cm)+0.2466\cdot Weight(kg)Common unit relationships used for display:
TBW(ft^3)=TBW(L)\cdot 0.0353147 \qquad\qquad TBW(m^3)=\frac{TBW(L)}{1000}A quick rule-of-thumb sometimes used is that TBW is roughly 50–60% of body weight in many adults, but this can be meaningfully higher or lower depending on age, sex, and body fat/lean mass.
- TBW is total body water
- Age is in years
- Height is in centimeters (cm)
- Weight is in kilograms (kg)
Total body weight is the sum of the weight of all the tissues, organs, and fluids in the body.
Total body water is the total amount of water present in an individual’s body.
Total Body Water Definition
Total Body Water (TBW) refers to the sum of all fluid within the body, including intracellular and extracellular fluids. It plays a crucial role in maintaining various physiological processes and overall health.
TBW serves as the primary medium for transporting nutrients, electrolytes, and oxygen to cells, while also facilitating the removal of waste products and toxins.
It helps maintain proper temperature regulation and aids in the lubrication of joints and organs. Additionally, TBW supports efficient digestion, absorption, and circulation.
The human body is often around 50–60% water in many adults, but TBW can vary depending on age, sex, body composition, and overall health. Infants tend to have a higher TBW percentage, while older individuals generally have a lower percentage due to changes in body composition.
Accurate measurement and maintenance of TBW are important for assessing hydration status and overall health. Excessive loss of TBW (dehydration) can lead to complications such as fatigue, dizziness, and impaired cognition, and can be dangerous in severe cases. On the other hand, excess TBW (fluid overload/edema) can cause swelling, shortness of breath, and strain on the cardiovascular system.
Total Body Water Example
How to calculate total body water (TBW)?
- Enter your details.
Enter your sex, age, height, and body weight (choose units as needed).
- Calculate TBW.
Press Calculate to estimate TBW (shown in liters by default) and view optional unit conversions and calculation steps.
FAQ
What factors influence Total Body Water (TBW) percentage?
Age, sex, body composition, and overall health status significantly influence TBW percentage. For example, infants typically have a higher TBW percentage than adults, and TBW often decreases with age. People with a higher body-fat percentage generally have a lower TBW percentage than those with more lean mass.
Why is maintaining TBW important?
Maintaining an optimal TBW supports nutrient transport, waste removal, temperature regulation, joint lubrication, and efficient digestion, absorption, and circulation. If you have medical conditions that affect fluid balance, discuss hydration and fluid goals with a clinician.
How can TBW be accurately measured?
TBW is most accurately measured with dilution techniques (often using tracer/isotope methods). Bioelectrical impedance analysis (BIA) can provide an estimate. DXA primarily measures body composition (fat, lean mass, bone) and may be used to infer related parameters in some contexts, but it does not directly measure total body water.
What are the consequences of TBW imbalances?
Dehydration (excessive loss of body water) can lead to fatigue, dizziness, impaired cognition, and can be dangerous in severe cases. Fluid overload/edema (excess body water) can cause swelling, shortness of breath, and cardiovascular strain, and should be evaluated by a healthcare professional.
