What’s the Buzz

Target BMI For Every Age

cartoon of man stepping on scale next to a doctor showing he is overweight

Body mass index (BMI) is a commonly used term. In fact, it’s been around for more than 150 years (it was developed in 1832 by a Belgian mathematician called LAJ Quetelet). Measuring your body mass index is a quick way to check if you are at a healthy weight. This article will explain how to measure your BMI and what is the healthy weight range for your height and age. 

What is body mass index (BMI)?

Body mass index (BMI) is the ratio of your height and body weight. It is an indirect measure of your body composition. Healthcare providers and the general public uses BMI as a rough estimate of body fatness. 

The higher your BMI number, the more body fat you have. Large amounts of body fat are linked to many serious medical conditions like heart disease, stroke, type 2 diabetes, and certain cancers. A low BMI can indicate anything from mild thinness to something more serious, like malnutrition or eating disorders.

While BMI loosely correlates to the amount of body fat versus lean body mass, it is not always an accurate way to diagnose a person’s health status. For example, someone with a healthy BMI may have high blood pressure, which would put them at risk of serious health complications. On the other hand, someone in the overweight or obese BMI categories may not have any significant health concerns at the present time. 

That’s why healthcare providers use BMI along with other parameters and risk factors to assess a person’s health risk. In general, however, you should aim for a body mass index in the healthy weight range. 

How do I calculate my BMI?

The formula to calculate BMI is to divide weight in kilograms (kg) by the square of a person’s height in meters (m2). 

If you are using U.S. units, divide the weight (pounds) by the square of height (inches) and multiply the result by 703. 

Therefore, if a person weighs 170 pounds and stands 68 inches tall, their BMI would be 170 ÷ 682 x 703 = 25.8.

If you don’t fancy doing the math, you can use this online tool (BMI calculator) to get your BMI value.

What is the normal BMI of the human body?

Healthcare providers classify body mass index (BMI) values in kg/m2 as follows:

  • Less than 18.5: Underweight
  • Between 18.5 and 24.9: Healthy BMI 
  • From 25 to 29.9: Overweight
  • Between 30 and 34.9: Class I obesity
  • From 35 to 39.9: Class II obesity
  • More than 40: Class III obesity

What is a good BMI for my age?

The interpretation of adult BMI does not change with age, gender, or race. In other words, the same BMI calculator and interpretation of results is used for a 20-year-old White woman and a 75-year-old Hispanic man. This is part of the reason why experts say that BMI is not the most accurate indicator of a healthy weight or a person’s overall health status.

In children, things are a little different. You use the same formula for calculating BMI in a child. However, the standard BMI chart should not be used to label overweight children or interpret the body mass index (BMI) in teenagers. The result should be interpreted according to the child’s age and gender. This is because the amount of body fat changes with age and is different in boys and girls. The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) have developed BMI-for-age growth charts that allow you to check a child’s percentile ranking. If a child’s BMI falls above the 95th percentile among children of the same age and gender, they are classified as obese. 

What does a high BMI mean?

As mentioned above, a normal BMI ranges from 18.5 to 24.9. If your BMI is outside this healthy range, you should talk to your healthcare provider. Keep in mind that if you are severely obese, even a 1-2 point drop in BMI value can significantly lower your risk of serious health conditions like cardiovascular disease and diabetes. People with a BMI that is considered overweight are at two times higher risk of developing diabetes compared to those with a normal weight and BMI in the optimum range. People with a BMI above 40 can have a 20 times higher risk of developing diabetes.

Remember that BMI uses height and weight to predict your health risks. It essentially compares your results to those of large populations. A high BMI does not automatically mean you are in poor health. However, it does put you at a significantly increased risk of serious health problems. That’s why it’s important to look at BMI, along with other factors like high blood pressure, high blood sugar, high cholesterol, diet, and physical activity. It’s also important to compare lean muscle mass versus body fat and measure waist size to assess your overall health status.

What can make body BMI inaccurate?


Muscle mass tends to decrease with age. As a result, older adults may have more body fat than their younger counterparts. However, a BMI in the high-normal to the overweight range for older adults may actually be a good thing. Some studies have shown a slightly higher BMI is associated with lower early-age mortality compared to people with an optimum BMI.

Race and ethnicity

The BMI calculator does not differentiate between different races and ethnic groups. However, research has shown that there are genetic and biological differences in muscle mass, fat distribution, and other factors among people of different races. 

For instance, Black women have a lower risk of metabolic diseases than White women with the same higher BMI values. On the other hand, people of Asian or Middle Eastern descent may be at high risk of metabolic diseases like diabetes even with lower BMIs.

Fat distribution

BMI calculations do not take a person’s waist circumference into account. Therefore, two people who are equally tall and weigh the same will have the same BMI. But if one of them has an apple or pear body shape (body types with fat distribution in the lower body), their risk for metabolic diseases and heart disease may be significantly higher. 

Muscle mass

Athletes have more lean muscle mass and less body fatness. They may fall in the overweight or obese BMI categories due to their muscle tissue mass, despite being in great general health. 

Wrapping up

Experts say that your lean muscle mass versus fat mass is a better indicator of your health status. However, because body mass index (BMI) is easy to calculate, it continues to be widely used as a measure of health. You should think of your BMI number as one piece of the puzzle. Use your BMI information along with other valuable metrics to get a sense of your overall health picture.


  1. https://health.clevelandclinic.org/is-bmi-accurate/?
  2. https://www.cdc.gov/obesity/basics/adult-defining.html?