Body Mass Index (BMI): Definition, overview and BMI Calculator

Healthy weight is very important in order to keep several health problems away. There are many Body Fat Measurement Methods including underwater-weighing and bioelectrical impedance.

However, these methods are more complicated and needs to be done under observation. Because BMI calculation formula is very simple, it can be used by anyone to determine the healthy weight.

What is Body Mass Index (BMI)?

Body Mass Index or BMI is a tool to measure a person’s body fat based on person’s height and weight. Though BMI does not directly measure the body fat levels, but it can give you the idea about how much person is healthy.

Many health professionals use BMI as screening tool to find out whether person is overweight, obese or a healthy weight.

Normal BMI number shows person has correct weight as per their height. At the same time, high number of BMI puts you at the risk of certain health conditions like high blood pressure, cholesterol, heart problems and diabetes.

On the other hand, if the person has low BMI, then it can lead to osteoporosis or anemia.

Let’s see how to calculate BMI.

What is my BMI?

Calculating BMI is very easy with just BMI charts and online BMI calculators. For this, you need to know about exact height and weight of you. If you’re not knowing it, then get it measured.

BMI Charts

BMI charts are the easy way to figure out your BMI. Look at the below table:

BMI Chart

Basically, you need to locate you exact height in inches on the left side of the chart. After that, move across the same line to find out your closer weight on the chart.

Stop at the point you find and see your BMI. The chart divides BMI into 4 categories – normal, overweight, obese and extreme obese.

For example, your height in inches is 60 and weight is 118 in that line, congrats! You are normal weight.

Find out your BMI falls into which category!

BMI calculation formula

So many online BMI calculators are available to answer your question – what is my BMI?

Manually calculating BMI formula is also possible. You just need to divide your weight with square of your height.

Normally 2 BMI formulas are there: Metric and Imperial.

BMI Metric Formula

In this formula, divide weight in kg with the square of height in meters (m2).

BMI = kg / m2

Generally, people measure their height in cm. so convert cm to m by this formula:

1 cm = 0.01 m

BMI Imperial Formula

BMI calculation formula will change a little bit with pounds and inches. Multiply the weight in pounds (lbs) by 703 and divide the result by the square of height in inches (in2).

BMI = lbs x 703/in2

Convert kg into pound by following formula:

1 kg = 2.205 pound

Avoid the math calculation by simply going for BMI charts or online BMI calculators. Calculate your BMI:

BMI for Adults

Adults of age 20 and older can find out their BMI by checking the standard weight categories. These are the same categories for both men and women of all body types and ages.

BMI Weight Status
Below 18.5 Underweight
18.5 – 24.9 Normal or Healthy Weight
25 – 29.9 Overweight
30 and above Obese

BMI ranges for Children and teens

While it may be true that BMI value has to do nothing with the age in adults, it’s not the same case for children and teens.

Although, you can calculate BMI with the same formula as adults, the result cannot have the same meaning.

In other words, children and teens have different amount of body fat with age as well as gender. So, the BMI number in children and teens depends on age and gender to figure out the status.

Percentiles are used to categorized different BMI weight groups based on age and gender. The reason is:

  • Amount of body fat changes with age.
  • Both, boys and girls produce it at different rates.
Percentile Weight Status
Percentile below 5th Underweight
5th percentile to less than the 85th percentile Normal or Healthy Weight
85th to less than the 95th percentile Overweight
95th and above percentile Obese

The Centers for Disease Control and Prevention (CDC) is providing gender-specific growth charts as well as BMI calculator for children and teens:

Find the charts here:

Girls of 2 to 20-years age group

Boys of 2 to 20-years of age group

And, the calculator here:

Understanding BMI measurements

Measuring BMI

For some people BMI gives accurate measure of body fat, while for others it may not.

For example, if you are an athlete, your BMI would be higher due to high muscle mass rather than body fat. In reality, they are not overweight and actually healthy and fit.

If you’re pregnant, BMI calculation may not work the same. Also, women have more body fat than men. Same for older people as they have more body fat than younger ones.

Plus, we have seen that BMI is not the same for children and teens as well.

So, understanding BMI measurements is equally important as it may not be a valid indicator if you have all above.

Health risks of high BMI

High BMI is also an indicator of health risks. As per studies, 1 out of every 3 adults is obese or overweight. In that case, weight loss is necessary to protect ourselves from major health issues.

Imbalance of energy intake and energy usage leads to weight gain. It’s important to lower down the BMI level if you’ve found yourself overweight or obese.

Some of the health risks of high BMI are:

  • Heart diseases
  • High blood pressure (hypertension)
  • Stroke
  • Type 2 diabetes
  • High blood cholesterol
  • Sleep apnea and snoring
  • Osteoarthritis
  • Cancers such as breast and colon cancer
  • gallbladder disease
  • Psychological stress

Contrarily, low BMI puts you at the risk of:

  • Osteoporosis
  • Frequently getting ill
  • Anemia
  • Premature births
  • Slow or impaired growth

Neither high nor low BMI is good for our health. The normal healthy weight is perfect for healthy and fit life.

If you’re underweight start eating healthy foods in order to gain healthy weight. Overweight or obese people can start doing some exercises or easy yoga poses from today itself.

Don’t worry if you see yourself in underweight or obese category. Make an appointment with a doctor and discuss the possible ways to gain healthy weight. Remember, you have to take care of yourself and only you can bring the change!