What is BMI and How to Calculate It

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After your last trip to the doctor's office, you may have heard from your doctor that you need to lower your BMI. Based on your height and weight, they have found that your BMI is too high and would like you to lose weight.

But, what is a BMI?

Body mass index was originally made to determine a person's body fat based on weight and height. However, your BMI does not actually measure the percentage of body fat.  

More: Understand Your BMI and Body-Fat Percentage

How to Calculate Your BMI

In the formula—which was developed in the early 19th century—you divide your body weight by your height squared. Then you times that by 703.

Or, you can use a chart or BMI calculator.

Your BMI score can give you a good idea on where you stand in the medical world, but is it an accurate way to know if you're overweight or not? There are many reasons why it may not be accurate.

More: Why You Should Step Off the Scale

Is BMI Accurate? 

Since height and weight are the only factors in the formula, it does not account for bone and muscle mass. Someone with more muscle mass and healthy body fat could have an overweight BMI score. On the other side of that, someone could have a normal BMI score but have too much fat and too little muscle on their body.

Because of the inaccuracies, other forms of measurement have emerged.

Body-Fat Caliper: This device measures the thickness of a fold of skin with an underlying layer of fat.

Bioelectrical Impedance Analysis: This method estimates body composition by monitoring the flow of an electrical current through bodily tissue.

Anthropometric: Translated from Greek as "measurement of man," this form of anthropology has been used to measure the physical variances in humans.

Hydrostatic Weighting: This technique looks at three variables when calculating body composition: the weight of the body outside of the water, the weight of the body fully submerged in water and the density of the water.

DEXA Scan: This technique looks at bone-mineral density with low doses of radiation.

More: 5 Ways to Test Your Body Composition

A Better Way

If you're not interested in more formulas, being submerged in water, or paying big bucks, you may want to try an easier way of measuring body fat. 

One of the easiest measurements is to use a pair of pants and top for comparison. Both should fit snug on your body. While improving your exercise and nutrition, try on the same pair of pants and top once every two weeks.

It will be a great motivation when those pants slide on a bit easier and you're not jumping up and down to get them on.

More: 3 Tips to Measure Fitness Health

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