Body Fat Percentage: BMI and Formulas

Body composition is a critical aspect of overall health and fitness. It refers to the relative amounts of fat, muscle, bone, and water in the body. A key component of body composition is body fat percentage, which is the proportion of fat your body carries relative to your total body weight. This blog post will focus on how body fat percentage is calculated using the Body Mass Index (BMI) and various formulas.

What is BMI?

Body Mass Index, or BMI, is a widely used tool to estimate body fat. This simple calculation is based on a person's weight and height. The BMI is calculated by dividing an individual's weight in kilograms by the square of their height in meters.

While BMI is a useful tool, it's important to note that it does not directly measure body fat. It is an indirect method of assessing body composition and has certain limitations. For instance, it might overestimate body fat in individuals with a high muscle mass, such as athletes.

Calculating Body Fat Percentage from BMI

Several formulas can be used to calculate body fat percentage from BMI. These formulas take into account an individual's gender and age, in addition to their BMI. Here are some of the most commonly used formulas:

  1. Deurenberg Formula: Body fat % = (1.20 x BMI) + (0.23 x age) - (10.8 x sex) - 5.4
  2. Deurenberg Modified Formula: Body fat % = (1.29 x BMI) + (0.20 x age) - (11.4 x sex) - 8.0
  3. Gallagher Formula: Body fat % = (1.46 x BMI) + (0.14 x age) - (11.6 x gender) - 10
  4. Jackson-Pollock Formula: Body fat % = (1.61 x BMI) + (0.13 x age) - (12.1 x sex) - 13.9

In these formulas, sex is coded as 1 for males and 0 for females.

Interpreting the Results

Once you have calculated your body fat percentage, you can use this information to assess your fitness level. It's important to remember that the ideal body fat percentage can vary based on factors such as age, sex, and individual health goals.

However, it's also crucial to understand that these formulas provide an estimate of body fat percentage. They should not replace a comprehensive health assessment by a healthcare professional.


Understanding your body fat percentage can provide valuable insights into your overall health and fitness. By using BMI and various formulas, you can get an estimate of your body fat percentage. However, it's important to remember that these are just tools and should be used in conjunction with other health assessments for a comprehensive understanding of your health.

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The Wellyme Team

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