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Body Mass Index (BMI) Calculator

A Body Mass Index (BMI) Calculator helps determine if one's weight is healthy or not. Get more information.

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Home / Health Insurance / Calculators / Articles / Body Mass Index Calculator

A Body Mass Index Calculator is a tool used to assess a person's body weight in relation to their height. It calculates BMI by dividing weight in kilograms by height in metres square. This measurement helps indicate if someone is underweight, normal weight, overweight, or obese, aiding in health assessments. Let’s breeze through this article and learn about the crucial details associated with BMI calculation and how the right calculator can help.  

Body Mass Index (BMI) Calculator
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Body weight alone may not be the best parameter to assess one's health. For instance, two people of the same age may have the same body weight but may not be equally healthy. For a tall person, a certain weight may be normal, whereas the same weight for a short person may be problematic. That is where the Body Mass Index comes into the picture.

Equations for calculating BMI
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International System of Units (SI)
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The Body Mass Index calculation formula is -

BMI = weight (kg) ÷ (height (m))²


For a 182 cm (1.82 m) individual whose weight is 80 kg,

BMI = 80 / (1.82 * 1.82) = 80 / 3.3124 = 24.16

Imperial System
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BMI = weight (lb) ÷ (height (inches))² × 703


For a 170-pound, 5'10" (70") individual whose weight is 80 kg,

BMI = (170 / 70*70) * 703 = (170 / 4900) * 703 = 24.42

What is Body Mass Index?
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Body Mass Index (BMI) is an estimated measure of your body fat. It is often used by healthcare providers as a tool to evaluate your body mass to evaluate any risk factors associated with high body mass, like diabetes, hypertension, heart disease, and stroke. BMI is not an accurate measure of how fat an individual is and is only a rough estimation of health. 

Your body mass comprises your muscles, fat, bones, and all your internal organs and components. BMI uses the ratio of your total body mass to your height as an estimation of your body fat content. This helps give an approximate idea of whether you fall in the healthy weight range or not. Healthcare providers use BMI as a screening tool to assess the likelihood of developing other chronic metabolic conditions. 

Understanding BMI Ranges for Adult Health
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The World Health Organization (WHO) provides recommended body weight classifications based on Body Mass Index (BMI) values for adults aged 20 or older. These classifications serve as indicators of health status regarding weight. Severe thinness is defined as a BMI below 16, indicating a significant lack of body fat and potential health risks. 

Moderate thinness falls within the BMI range of 16 to 17, followed by mild thinness from 17 to 18.5. A BMI of 18.5 to 25 is considered normal, reflecting a healthy weight range. 

Beyond this, individuals enter the overweight category with a BMI of 25 to 30, followed by obese classifications: Class I (30-35), Class II (35-40), and Class III (over 40).

Interpreting BMI for children and teens
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BMI, or Body Mass Index, serves as a crucial tool for assessing weight-related health risks in both adults and children. However, interpreting BMI for children and teenagers requires a nuanced approach, taking into account their age and sex-specific growth patterns. While the calculation formula remains the same as for adults, the interpretation and classification differ due to variations in body composition during growth and development stages.

Age and Sex-Specific considerations
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Children and teens undergo significant physical changes as they grow, affecting their body fat distribution and overall BMI. Therefore, BMI assessments for this demographic must consider age and sex-specific factors to accurately reflect their growth trajectory and health status.

To address these differences, the Centers for Disease Control and Prevention (CDC) developed BMI-for-age growth charts. These charts provide a visual representation of BMI percentile rankings based on age and sex. By comparing a child's BMI to these charts, healthcare professionals can determine where they fall in relation to their peers.

Defining obesity in children and teens
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Obesity in children and teens is defined based on BMI percentile rankings. A BMI at or above the 95th percentile of children of the same age and sex in a reference population indicates obesity. For instance, a 10-year-old boy with a BMI placing him in the 95th percentile would have a BMI greater than that of 95% of boys of similar age and sex.

Consider a 10-year-old boy of average height and weight. If his BMI places him in the 95th percentile, it indicates that he is obese according to CDC guidelines. This percentile ranking reflects his BMI compared to that of his peers, highlighting potential weight-related health risks.

How to find out your BMI
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You can find out your Body Mass Index by using a BMI calculator, such as the one available on the Centers for Disease Control and Prevention’s website. 

You have to ensure the parameters are in the correct units. Enter your weight in kilograms and height in metres, or weight in pounds and height in feet and inches.

Here is the revised range of reference of BMI for a South Asian population for you to understand if you are at a healthy weight or not.

Nutritional Status

Body Mass Index 


Less than 18.5


18.5 to 22.9


23 to 24.9

Obesity Type 1

25 to 29.9

Obesity Type 2

More than 30

Having a BMI less than 18.5 may indicate that an individual is more prone to the following. 

A higher BMI puts one at more risk for the following. 

BMI is not an accurate tool for risk assessment. There are multiple other factors that have established direct causative relation to the above disorders that take precedence over BMI. Here it is only used as a screening tool. Not every individual with a high BMI has a high body fat percentage.

The Role Of BMI In Assessing Body Fatness
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Body Mass Index (BMI) is a widely used metric for assessing body fatness and overall health status. While BMI provides valuable insights, its correlation with body fatness is subject to various factors, requiring a nuanced understanding of its limitations and applications.

Despite having the same BMI, women generally possess more body fat than men. This discrepancy stems from biological differences in fat distribution and composition between genders. Consequently, BMI may not accurately reflect body fatness when comparing individuals of different sexes.

Ethnic and racial variances
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BMI's effectiveness as an indicator of body fatness can vary among different racial and ethnic groups. Factors such as genetic predispositions and cultural practices influence body composition, leading to variations in the relationship between BMI and actual body fat content.

Age plays a significant role in body fat distribution and composition. Older adults, on average, tend to have higher levels of body fat compared to younger individuals with the same BMI. This age-related difference underscores the importance of considering age-specific factors when interpreting BMI values.

Impact of Athleticism on BMI
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Athletes often exhibit lower levels of body fat compared to non-athletes with the same BMI. Their higher muscle mass contributes to a higher BMI, yet their lower body fat percentage suggests superior overall fitness and health. Thus, BMI alone may not accurately reflect body composition in individuals with high levels of physical activity.

The accuracy of BMI as an indicator of body fatness is higher in individuals with elevated BMI levels. Those with very high BMIs, such as 35 kg/m2, are more likely to have high body fat percentages. However, individuals with moderately high BMIs may have varying body compositions, including high lean body mass (muscle and bone) rather than excess fat.

Points to remember
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There are several conditions in which BMI may not be an accurate measure. Here are some reasons why. 

Frequently Asked Questions
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Here’s a list of common questions and answers related to BMI calculators.


Why is having a healthy BMI important?

On average, people with a healthy weight and BMI are less likely to develop metabolic conditions like diabetes, hypertension, and heart disease in the long run. They are also less likely to get chronic joint pain and have better sleep.

What should I do if my BMI is too high?

If your BMI is higher than the normal range, your doctor may suggest that you lose weight (especially if you have weight around the abdomen). This can be achieved by eating sufficient fruits, vegetables, and protein, regular exercise including both cardio and strength training, and a regular sleep schedule.

What should I do if my BMI is too low?

If you are underweight, you may need to take a close look at your diet and assess if you are eating enough. You can gain weight in a healthy manner by introducing more complex carbohydrates and protein rather than opting for saturated fats or desserts. Strength training may also help.

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.