What is BMI?

You’ve heard the term and know it’s some sort of measurement, but do you know what BMI really is?

Simply put, BMI or Body Mass Index is the approximation of the amount of fat on your body. It gives you and your doctor an estimation of how your body is composed and can serve as an indicator of potential health risks. So, how do you figure out your BMI and what’s an ideal BMI number to have? Let’s break it down.

The BMI Basics: What is BMI?

As I mentioned, BMI stands for Body Mass Index. For adults, your BMI number is determined by your age and your weight. A BMI number of 18.5 and lower is considered underweight while a score of 25 to 29.9 is considered overweight and anything 30 and over is considered obese.

Here are the numbers:

  • Underweight – BMI number of less than 18.5
  • Normal Weight – BMI number of 18.5 to 24.99
  • Overweight – BMI number of 25 to 29.99
  • Obese – BMI number of 30 or more


There are some relatively easy formulas that you can use to calculate your BMI if you feel like exercising your brain. You can also use this handy dandy online BMI calculator, as well.

In the US:

BMI = (Your weight in pounds x 703) / height in inches²

Metric Version:

BMI = Weight in kilograms / height in meters²

If you just tried the formula and discovered that your BMI number is higher than you anticipated, stop! Don’t panic! Because while the BMI chart and numbers are all well and good at determining possible health risks associated with excess body fat like heart disease, high blood pressure, Type 2 Diabetes, etc., they don’t do such a good job with taking into consideration other factors.

If you’re an athlete or have a lot of muscle, for example, chances are that your number is going to indicate that you’re overweight or even obese. The simple formula doesn’t take into account anything other than a “normal amount “ of muscle mass and sees that extra weight as fat. The BMI formula can also under-indicate fat in the elderly or those who have lost a lot of muscle.

But here’s the thing, if you know you have a few (or 50 pounds to lose), you know you have that weight to lose. You know you’re not going to have a healthy BMI number, so don’t try to make excuses for it. You’re so much more than a number, but it’s a good idea to keep an eye on where you fall on the chart if for no other reason than to not be surprised when your doctor brings it up.


So, how do you bring your BMI number down to a normal range? Diet and exercise, my friend. Making healthy food choices, exercising 3-5 times a week, and increasing your general activity overall. I promise that it’s worth it to start working on you. And, if you need that number as motivation as something to beat, than use it as motivation. If it discourages you, put it in the back of your mind and go exercise and eat something healthy anyway.

BMI is not the end all, be all number, but it is a good indication of how you’re doing health-wise. Get up and go exercise. You’re worth it!

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