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Calculate Your BMI

BMI stands for Body Mass Index. Body mass index (BMI) is a measure of body fat based on height and weight that applies to both men and women.

Calculating your BMI helps you determine whether you may be overweight and helps assess your risk for developing obesity-related diseases. You may think—Hey, I’m young, I don’t have to worry about this!—but the truth is more and more youth are becoming overweight in their teens and this is jeopardizing their long-term health. That’s why it’s important to know your numbers and what they mean.

How to Calculate Your BMI

In order to calculate your BMI, you will need to know your height and your weight. Use the BMI calculator or tables to estimate your total body fat.

Here’s what your score means:

	BMI
Underweight	Below 18.5
Normal	18.5 – 24.9
Overweight	25.0 – 29.9
Obesity	30.0 and Above

You should know that there are limitations to the BMI calculation in assessing your total body fat and overall weight health. First, these calculations are based on heights and weight for adult men and women. As a teen, you are still growing and may have a BMI that indicates you are underweight or overweight, when in fact your body mass is still in the process of stabilizing. Second, it may overestimate body fat in athletes and others who have a muscular build. That’s why when using the BMI calculation to assess whether you are overweight, you should also consider other factors.

Other factors

According to the National Heart, Lung, and Blood Institute’s Obesity Education Initiative guidelines, assessment of overweight involves using three key measures:

body mass index (BMI)
waist circumference, and
risk factors for diseases and conditions associated with obesity.

You have already learned how to calculate your BMI. Your waist circumference measures abdominal fat which is another predictor of your risk for developing obesity-related diseases. To calculate your waist circumference, place a measuring tape around your waist. Risk increases with a waist measurement of over 40 inches in men and over 35 inches in women.

Here’s a breakdown of your disease risk for developing type 2 diabetes, hypertension, and CVD based on your based on your BMI and waist circumference measurements. Even if you are normal weight, increased waist circumference can mean increased disease risk.


	BMI (kg/m²)	Obesity Class	Men 102 cm (40 in) or less Women 88 cm (35 in) or less	Men > 102 cm (40 in) Women > 88 cm (35 in)
Underweight	< 18.5		–	–
Normal	18.5 – 24.9		–	–
Overweight	25.0 – 29.9		Increased	High
Obesity	30.0 – 34.9	I	High	Very High
	35.0 – 39.9	II	Very High	Very High
Extreme Obesity	40.0 +	III	Extremely High	Extremely High

Additional Risk Factors

It’s not just about the numbers when assessing your risk for developing obesity-related diseases. It also depends on your family health history. Do your parents, siblings, aunts, uncles, or grandparents have any of these additional risk factors?

High blood pressure
High cholesterol
High sugar
Heart disease
Physical inactivity
Cigarette smoking

If so, then you may be at greater risk. For people with a BMI greater than or equal to 30 or those with a BMI of 25 to 29.9 and have two or more risk factors, the National Heart, Lung, and Blood Institute recommends weight loss. Even a small weight loss can help lower your risk of developing diseases associated with obesity.

Why this Matters

Obesity-related diseases kill TK Americans every year. TK youth in American are considered overweight. Weight health isn’t just about looking good—it’s also about feeling good and having a better quality of life. If you’ve determined that you need to get fit, we’re here to help you develop your own diet and fitness plan. Click here to get started.