What is Body Mass Index (BMI)?

What is Body Mass Index (BMI)?

Body Mass Index (BMI) indicates whether a person is underweight, overweight, obese, or a healthy weight for their height. It measures body fat based on height and weight and applies to most adults over 20. For those under 20, the overall percentile is the best assessment of body fat.

However, body mass index fails to account for a person’s frame, muscle mass, and other organic material such as fat, bone, cartilage, and water weight. Another problem is that athletes, children, and older people can contribute to an inaccurate calculation, indicating that they may be underweight or overweight when they are not. Also, not everyone around the world uses the same measurements or categories. Therefore, BMI should not be used as a diagnostic tool but only as a guideline. Despite these variations, it is widely regarded as an adequate measurement for many people.

You can check your body mass index in two ways without using any special equipment. All you need is your height and weight. Then, you can look it up on a chart or plug numbers into a calculator.

Using BMI Charts to determine Body Mass Index

Below is an example of a BMI chart. The top and right margins have pounds and inches for those who use imperial measurements, and the left and bottom margins have meters and kilograms for those who use the metric system.

To determine your body mass index, locate your height. Then, move your finger to the left or right until it lines up with your weight.

BMI Chart by nagualdesign (CC BY-SA 4.0)

Body mass index is different for children. It uses the same calculation as adults but then compares the percentile values for boys or girls of the same age. The child is underweight if the result is less than the 5th percentile. If it is above the 95th percentile, a child is obese. Children between the 85th and 95th percentile are considered to be overweight.

Can you trust Body Mass Index?

Even though the body mass index fails to account for a person’s frame, muscle mass, and age, and some countries’ standards and recommendations differ, the body mass index remains one of the most popular tools for estimating whether a person is underweight, overweight, obese, or a healthy weight for their height. Regardless, maintaining a weight in the normal range is better for your overall health than being overweight or obese.

However, it would be best to talk with your doctor, dietitian, or other health professional about what may be best for you.

The Takeaway

Knowing your BMI is an excellent place to start if you want to lose weight, get in shape, or maintain a healthy weight. Talking with a health professional and keeping a journal to track your progress will increase your chances of success.


FitTrend’s mission is to help you along your self-improvement journey, promote an active lifestyle, and help you achieve your goals. Our journal can help you track your weight. Also, FitTrend allows you to connect certain scales to your account to make it easier for you to track your weight automatically. Create your account today and start using FitTrend for free!

Disclaimer: No content on this site should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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