If you’ve ever had a physical check-up, you’ve probably been told what you BMI was. But do you know what BMI actually is? BMI stands for Body Mass Index.

It is a scale health professionals use to measure fat based on how your weight relates to your height. It applies to most adults aged 20 or older.

BMI is most often used as a screening tool to indicate if a person is at their ideal weight for their height or if they are underweight, overweight or obese. It helps health professionals determine if a person’s health risks are increased because of their weight.

A BMI test is simple and inexpensive, and is a non-invasive way to measure body fat. It’s a reasonable indicator of body fat in both adults and children.

BMI in children and adolescents between 2-20 years old is interpreted in relation to the child’s age and gender.

How to Calculate Your BMI

You can measure your BMI via online calculators at many health websites including www.WebMD.com. The basic body mass index equation is fairly simple.

To work out your body mass index manually, divide your weight in pounds by your height in inches squared. Then multiply the results by a conversion factor of 703. You can also use kilograms and meters in place of pounds and inches.

The formula is: BMI = weight in pounds / [height in inches x height in inches] x 703

So for example, someone who weighs 150 pounds and is 5 feet 6 inches tall has a BMI of 24.

According to the charts, if your BMI is less than 18.5 you are underweight. Those with a BMI of 18.5 to 25 are at their ideal weight while those between 25 and 30 are overweight.

People with a BMI over 30 are considered obese.

Pros of BMI

Figuring your BMI is simple and inexpensive. It can be done manually or with online calculators, as mentioned. BMI calculations can be done at home or anywhere you have access to the internet. Body mass index is usually an accurate estimate for determining obesity.

Cons of BMI

One drawback to BMI measurements is that it doesn’t account for a person’s waist, hip or chest measurements, or bone density. Nor does it factor in such things as age, sex, ethnicity and muscle mass.

If you have a large amount of muscle mass, you might end up with a high BMI while in reality you are healthy and carry very little excess fat.

BMI can underestimate the health risks of someone who is at a normal weight but may carry more fat than is healthy.

Overall, your BMI is a simple way to measure your body fat in relation to your height and weight. It’s a good way to determine if you need to look at losing weight to reduce your risk for health problems.