What is Body Mass Index? (BMI)

Body weight can be a sensitive topic. After all, it’s often directly tied to things like body image, self-esteem and mental health. But asking yourself, “How much should I weigh?” can be an important step in taking control of and improving your health. The numbers on the scale don’t define you, but they can cause some major health concerns. Read on to learn about body mass index (BMI) and when to see a doctor.

What is BMI and why does it matter?

BMI is your weight in pounds (lbs) divided by height in inches (in) squared then multiplied by a conversation factor of 703. This measures your body fat relative to how tall you are to help determine possible risk of weight-related health problems, like type 2 diabetes or cardiovascular disease.1

BMI can be used as a screening tool rather than a diagnostic test . That means it doesn’t diagnose body fat or someone’s overall health. Consider your BMI an indirect indicator that may help determine how healthy your weight is for your unique body size and shape. If your doctor is concerned with your BMI, they can do follow-up assessments to dive deeper into your heath. These assessments can include calliper testing to determine skinfold thickness, as well as evaluations of diet, exercise and family history.1

Knowing your BMI may help you stay on top of your weight before you start to experience potential health conditions. Think of it as a preventive measure, like any other screening tool.

How do I use a BMI calculator?

Luckily, there’s no need to get out a pen and paper — or use mental math to calculate your BMI. You can simply use a BMI calculator to figure out your numbers. But in case you'd like to see how everything is broken down, check out the example below. It shows how the original formula is used in a sample calculation.

  • Formula: Weight (lb.) / [Height (in.)]2 x 703
  • Sample person: Weight = 150lbs., Height = 5 ft. 5 in. (65 in.)
  • BMI calculation: [150 ÷ (65)2] x 703 = 24.96

What’s a healthy BMI?

If you’ve wondered, “Am I overweight?”, a quick BMI check is an easy way to get some answers. To find out whether your BMI is considered healthy, read through the standard BMI calculator chart below. Think of this chart as a reference for adults 20 years and older — while realizing there are some factors it does not include, like whether you’re male or female and your ethnicity. Those factors could change the chart results for you, so if you want more precise information, check in with your doctor.1

Based on the sample calculation above, it looks like someone with a height and weight like the one in the example would have a BMI that’s at the upper limit of the healthy weight status range.

It’s important to remember there’s no ideal weight for women or men. Instead, think of weight as one potential indicator of overall health, and remember everyone’s body is different. Two bodies that look completely different can both be healthy.

Adult BMI

Weight status

Below 18.5






30.0 and above


For children and teens, age and sex are additional factors used to determine BMI. This is because the amount of body fat changes with age and varies between boys and girls in those younger years of life.

When should I see my doctor about my weight?

If you’re concerned about your weight, make an appointment to see your primary care provider (PCP). Bring a list of questions and concerns, and a list of family health history. After a discussion, your doctor may talk through next steps if they think you’re at risk of weight-related health problems. For example, they may recommend focusing on lifestyle habits like eating healthy and moving your body.