What Is Body Mass Index and How Do You Calculate It?

Body Mass Index

Body mass index (BMI) is a measure of body fat based on height and weight that is used to determine whether a person is underweight, normal weight, overweight, or obese. It is calculated by dividing a person's weight in kilograms by the square of their height in meters.

The World Health Organization (WHO) defines the following categories based on BMI:

• Underweight: BMI less than 18.5

• Normal weight: BMI of 18.5 to 24.9

• Overweight: BMI of 25 to 29.9

• Obesity: BMI of 30 or higher

It's important to note that BMI is not a perfect measure of body fat and may not be accurate for everyone. For example, people who have a lot of muscle mass may have a high BMI even though they have a low amount of body fat. Similarly, people who have a low amount of muscle mass may have a low BMI even though they have a high amount of body fat.

Therefore, it's important to consider other factors in addition to BMI when assessing a person's weight and health status. These may include waist circumference, body fat percentage, and overall health and wellness. It's always a good idea to talk to a healthcare provider about your weight and any concerns you may have.

BMI Formula Description

The body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It is calculated by dividing your weight in kilograms by your height in meters squared (BMI = weight (kg) / height (m)^2).

Example:

For example, if you weigh 70 kilograms and are 1.75 meters tall, your BMI would be 70 / (1.75^2) = 22.9.

Here is the BMI formula in different units:

• Weight in pounds / (height in inches x height in inches) x 703

• Weight in kilograms / (height in meters x height in meters)

BMI Calculator Information

To calculate your body mass index (BMI), you will need to know your weight in kilograms and your height in meters. To convert your weight from pounds to kilograms, divide your weight in pounds by 2.2. To convert your height from inches to meters, multiply your height in inches by 0.0254.

Once you have your weight in kilograms and your height in meters, use the following formula to calculate your BMI:

BMI = weight (kg) / height (m)^2

For example, if your weight is 150 pounds and you are 5'5" (65 inches), your BMI would be calculated as follows:

First, convert your weight to kilograms: 150 pounds / 2.2 = 68.18 kilograms

Next, convert your height to meters: 65 inches * 0.0254 meters/inch = 1.651 meters

Finally, calculate your BMI: 68.18 kilograms / (1.651 meters)^2 = 24.96

A BMI of 18.5 to 24.9 is considered normal, a BMI of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is considered obese. However, it's important to note that BMI is not a perfect measure of health, as it does not take into account differences in muscle mass, bone density, and distribution of fat. It is always best to speak with a healthcare provider to determine the best weight range for your specific situation.

5 Examples BMI Calculation 

Example 1

A person who is 5 feet, 5 inches tall (65 inches) and weighs 140 pounds has a BMI of 22.4. Here's how to calculate it:
BMI = (140 pounds) / (65 inches)^2 x 703
= 22.4


Example 2
A person who is 6 feet tall (72 inches) and weighs 200 pounds has a BMI of 27.8. Here's how to calculate it:
BMI = (200 pounds) / (72 inches)^2 x 703
= 27.8


Example 3
A person who is 5 feet, 2 inches tall (62 inches) and weighs 110 pounds has a BMI of 19.5. Here's how to calculate it:
BMI = (110 pounds) / (62 inches)^2 x 703
= 19.5


Example 4
A person who is 5 feet, 8 inches tall (68 inches) and weighs 150 pounds has a BMI of 22.0. Here's how to calculate it:
BMI = (150 pounds) / (68 inches)^2 x 703
= 22.0


Example 5
A person who is 6 feet, 2 inches tall (74 inches) and weighs 180 pounds has a BMI of 24.4. Here's how to calculate it:
BMI = (180 pounds) / (74 inches)^2 x 703
= 24.4