Total Body Water (TBW) Calculator

Estimates the volume of water in the body by two gender specific formulas for adults and one for children.

Refer to the text below the calculator for more information about the formulas employed to determine TBW.


Body water is defined as the water content in the tissues, blood, bones and elsewhere in the body. All the percentages of body water sum up to total body water (TBW).

This water has numerous metabolic roles within and outside the cells. Ensuring this value remains constant and within healthy limits is part of homeostasis.


The most commonly used rough estimate of body water is based on the rule that the average human adult body consists of approximately 60% water, thus we are able to deduct TBW via a person’s weight.

However, several studies have designed different gender specific equations that allow for TBW estimates based on more specific data, such as age and height.

Watson Formulas

  • Male TBW = 2.447 - (0.09156 x age) + (0.1074 x height) + (0.3362 x weight)
  • Female TBW = -2.097 + (0.1069 x height) + (0.2466 x weight)

Hume-Weyers Formulas

  • Male TBW = (0.194786 x height) + (0.296785 x weight) - 14.012934
  • Female TBW = (0.34454 x height) + (0.183809 x weight) - 35.270121

Mellits-Cheek Formulas (for children)

  • Boys TBW (height < 132.7 cm) = -1.927 + 0.465 x weight + 0.045 x height
  • Boys TBW (height > 132.7 cm) = -21.993 + 0.406 x weight + 0.209 x height
  • Girls TBW (height < 110.8 cm) = 0.076 + 0.507 x weight + 0.013 x height
  • Girls TBW (height > 110.8 cm) = -10.313 + 0.252 x weight + 0.154 x height

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Water percent of body weight (%)*
* H2O % of body weight for females is 50-55% whilst for males 60%.
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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


 

Total Body Water (TBW) Explained

Body water is defined as the water content in the tissues, blood, bones and elsewhere in the body. All the percentages of body water sum up to total body water (TBW). Ensuring this value remains constant and within healthy limits is part of homeostasis.

The most commonly used rough estimate of body water is based on the rule that the average human adult body consists of approximately 60% water, thus we are able to deduct TBW via a person’s weight.

However, several studies have designed different gender specific equations that allow for TBW estimates based on more specific data, such as age and height.

Watson Formulas

  • Male TBW = 2.447 - (0.09156 x age) + (0.1074 x height) + (0.3362 x weight)
  • Female TBW = -2.097 + (0.1069 x height) + (0.2466 x weight)

Hume-Weyers Formulas

  • Male TBW = (0.194786 x height) + (0.296785 x weight) - 14.012934
  • Female TBW = (0.34454 x height) + (0.183809 x weight) - 35.270121

Mellits-Cheek Formulas Specifically Designed for Use in Children

  • Boys TBW (height < 132.7 cm) = -1.927 + 0.465 x weight + 0.045 x height
  • Boys TBW (height > 132.7 cm) = -21.993 + 0.406 x weight + 0.209 x height
  • Girls TBW (height < 110.8 cm) = 0.076 + 0.507 x weight + 0.013 x height
  • Girls TBW (height > 110.8 cm) = -10.313 + 0.252 x weight + 0.154 x height

A new born’s body weight is made up of nearly three-fourths of water, but this percentage starts to decline up until the first birthday, and then continues, at a slower rate, as we age. One of the reasons why is due to people developing more body fat and less fat-free mass as they age.

Water percentages in infants are as follows:

  • Birth to 6 months: Average TBW: 74%; Range 64 – 84%;
  • 6 – 12 months: Average TBW: 60%; Range 57 – 64%;
  • 12 – 24 months: Average TBW: 60%; Range 49 – 75%.

The table below summarizes several reference values for TBW in children and adults:

Adults 12 – 18 years 19 – 50 years > 51 years
Average Range Average Range Average Range
Male 59% 52-66% 59% 43-73% 56% 47-67%
Female 56% 49-63% 50% 41-60% 47% 39-57%

Water is stored in two main body compartments:

  • Intracellular fluid (ICF): the fluid within cells covers 2/3 of TBW;
  • Extracellular fluid (ECF): the fluid outside the cells covers the remainder 1/3 of TBW.

Body water fulfils several crucial roles, such as:

  • Is the key cellular nutrient;
  • Metabolizes and transports proteins and carbohydrates;
  • Is essential part of thermal regulation;
  • Provides a vehicle for eliminating waste (urine);
  • Is part of the fluid protecting the brain and spine;
  • Is part of amniotic fluid in pregnancy.
 

References

Original reference

Watson PE, Watson ID, Batt RD. Total body water volumes for adult males and females estimated from simple anthropometric measurements. Am J Clin Nutr. 1980 Jan;33(1):27-39.

Hume R, Weyers E. Relationship between total body water and surface area in normal and obese subjects. J Clin Pathol. 1971; 24:234-238.

Validation

Mendley SR, Majkowski NL, Schoeller DA. Validation of estimates of total body water in pediatric dialysis patients by deuterium dilution. Kidney International. 2005; Volume 67, Issue 5, Pages 2056–2062.


Specialty: Fitness

Article By: Denise Nedea

Published On: June 12, 2020

Last Checked: June 12, 2020

Next Review: June 12, 2025