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How To Measure Body Mass Index

By Edited Nov 13, 2013 2 5

A BMI Chart

A BMI Chart
Credit: liposonix.com

What Is Body Mass Index?

So you've probably heard about body mass index before. Whether your doctor told you your body mass index right after you've been weighed or your friend's have been talking about their BMI, you are probably anxious about what this means.

Body mass index or BMI is a weight to height ratio. Your body mass index tells you how many kilograms of fat are in a cubic meter of your body. For example: if you have a BMI of 20 it means you have 20 kilograms of fat in one square meter of your body. It's basically a body fat measurement that's similar to calculating body fat percentage.

How To Calculate Body Mass Index

BMI is a simple formula that can be easily memorized. The formula is the same for everyone whether you are male, female, old, young, sedentary, athletic, muscular, etc. The formula is:

(Weight in pounds*705) ÷ (Height in inches÷Height in inches) = BMI

Here are the steps to calculating it:

1. Take your weight in pounds

2. Now multiply it by 705. You'll get a huge number. Save this number.

3. Take your height and convert it to inches. (Example: 5 feet= 60 inches)

4. Take that huge number you had from step #2 and divide it by your height in inches. You should now have a smaller number.

5. Now divide that number again by your height in inches. That number will be between 15-50 roughly.

6. You should now have your BMI.

See below to see what category your weight falls under.

Body Mass Index categories

Now take your BMI and match it up with the category below.

BMI                              category

>17.5                            Emaciated

17.5-18.5                     Underweight

18.5-25                        Normal Weight

25-30                           Overweight

30-40                           Obese

40+                              Extremely Obese

What Do These Categories Mean?

Emaciated: You are either very underweight or at risk of developing an eating disorder such as anorexia or bulimia. Emaciated is another word for starving so please consult your doctor to try to gain weight back or gain weight back in muscle.

Underweight: You are slightly underweight but not starving. You don't have to do much but watch your weight and if you see unusual amounts of weight loss consult your doctor. People in this category are typically 5-10 pounds under the average weight.

Normal Weight: This is the healthiest category. If you are in this category, maintain your weight and keep up the good lifestyle. If you are closer to the 25 BMI mark then try losing a few pounds.

Overweight: You are a few pounds overweight. Typically this will mean you'll need to lose 5-30 pounds but it depends on the person. Nothing major is required but try eating healthier, cutting out junk food, and exercising more. Monitor your weight and make sure it doesn't increase.

Obese: You are more than overweight. You'll need to make some lifestyle changes such as going on a diet and cutting out junk fatty foods. Look into some new exercise programs, healthier foods, and diets. You will typically be at least 50 pounds overweight if you are in this category.

Extremely Obese: You are very unhealthy. Please consult a doctor to discuss ways to lose large amounts of weight. If you are in this category than you might need to lose around 100+ pounds but it will depend on the person. You might also be at risk of developing binge eating disorder.



Mar 30, 2013 4:21am
Great article. You've put some very pertinent simple information at the fingers of those who may need it most. Thumbs up and keep em coming.
Mar 30, 2013 10:26am
This is a great article. On my Wii Fit it always measures it but I didn't know how it was calculated. I just did the calculation and it matches what is on my Wii Fit. Thanks!
Mar 30, 2013 10:57am
Thanks for such an informative article
Mar 30, 2013 1:40pm
I've seen the chart before but I've never known the formula to calculate it. Apparently I'm emaciated :/
Mar 31, 2013 12:44pm
Adistin 1996, your article is terrific. I love the way you put your chart at the beginning of your article. It is easy to understand and learn from. Thank you for educating people about Body Mass Index. You broke it down in simple terms and explained how it is calculated. I would recommend that you write more articles about this subject. Great job!
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