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BMI Calculator: Accuracy, Limitations, and Better Alternatives for Body Composition

Writer's picture: Adil HANAFIAdil HANAFI

BMI Carved On Apple


Introduction: Why Your Weight Should Match Your Height


Maintaining a healthy weight does more than just boost your energy levels and improve your appearance. When your weight is proportional to your height, you can enjoy numerous benefits:


  • Improved sleep quality

  • Greater ability to participate in activities you love

  • Reduced joint and muscle pain

  • Lower risk of heart disease and certain cancers

  • Enhanced overall well-being

  • Many other benefits 



To categorize individuals into different weight ranges (underweight, normal weight, overweight, and obese), healthcare professionals often use Body Mass Index (BMI) as a reference point.



The Origin of BMI


In the early 19th century, BMI was developed by Adolphe Quetelet, a Belgian mathematician, astronomer, and statistician. It serves as a simple method to assess obesity levels in the general population and aids in formulating public health policies.



How to Calculate BMI (Body Mass Index)


To calculate BMI, you divide your weight in kilograms by the square of your height in meters or divide your weight in pounds by the square of your height in feet:


  1. Metric: BMI = weight (kg) / (height (m))²

  2. Imperial: BMI = (weight (lbs) / (height (inches))²) × 703




BMI Calculation Equation



BMI Categories for Adults


The standard ranges of BMI (Body Mass Index) typically used to classify adults are as follows:

  • Underweight: BMI less than 18.5

  • Normal weight: BMI 18.5 to 24.9

  • Overweight: BMI 25 to 29.9

  • Obesity:

  • Class 1: BMI 30 to 34.9

  • Class 2: BMI 35 to 39.9

  • Class 3 (Severe or Morbid Obesity): BMI 40 and above


Example BMI Calculation


For a woman weighing 68 kg with a height of 1.70 m:

 BMI = 68 / (1.7)² = 23.53

Result: Normal weight range



How Accurate is BMI?


While BMI is widely used, it has several limitations:

  1. Muscle mass: BMI doesn't differentiate between lean body mass (muscle, bone, water) and fat mass. Athletes or individuals with high muscle mass may have a high BMI that doesn't accurately reflect their body fat percentage.

  2. Age considerations: BMI might be less reliable for older individuals due to age-related muscle mass loss.

  3. Body fat distribution: BMI doesn't account for where fat is stored in the body, which can be a crucial factor in assessing health risks.



BMI and Pregnancy


BMI can give a basic idea of weight during pregnancy, but it's not always accurate because pregnancy changes the body a lot. The body retains more fluids, the uterus grows, and weight gain happens in different places—like fat, muscle, and fluids.

Doctors use more than just BMI to check on general health and the baby's development. They watch weight gain, measure around the belly, and check things like blood pressure and blood sugar levels to ensure everything is going well.


Better Alternatives to BMI for Assessing Health


For a more comprehensive health assessment, consider these methods:

  1. Body composition analysis

  2. Body circumference measurements (hip, waist, thighs, shoulders, neck)


These techniques provide more detailed information about:

  • Body fat percentage

  • Muscle mass

  • Fat distribution


They are particularly useful for:

  • Athletes

  • Older adults

  • Individuals with unique body types


To help you achieve a more accurate body assessment, we’ve developed an app that can give you the above-mentioned measurements and more. Using Fitycal App, you can have the following body measurements:


  • Body fat %

  • Lean Mass %

  • Fat Mass

  • Lean mass

  • Waist-to-Hip Ratio

  • Neck Circumference

  • Shoulders Circumference

  • Upper Chest Circumference

  • Chest Circumference

  • Waist Circumference

  • Hips Circumference

  • Biceps Circumferences

  • Thighs Circumferences

  • Calfs Circumferences


Make sure to request access to the BETA version, and be one of the very first to access this new technology for free.


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