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By using this BMI calculator, you can discover whether you are a healthy weight for your height or not. It can be used for most adult men and women over the age of 20.

But what is BMI and how can you find out your BMI on your own? Here we explain everything you need to know in this comprehensive guide.


Why use a BMI calculator?

Your BMI is an easy and efficient way to measure your body composition. And using a calculator is the quickest way to find out your number.

Plus, as you adjust the weight, you can instantly see the effect it has on your BMI equivalent. This is a good indicator of how much weight you might need to gain or lose if your BMI is not in the healthy range.

What is BMI?

BMI, short for body mass index, is a measure of body fat based on your weight in relation to your height.

BMI is based on a formula, meaning it is not a direct measurement of body fat. But, research shows that it correlates well with more direct measures like dual-energy X-ray absorptiometry (DEXA) scans and underwater weighing.

BMI is also an easy and inexpensive alternative to these more complex measurement options.


As well as measure body fat, BMI can be an indicator of your risk for diseases that are linked to being overweight or obese.

It is often used as a screening tool for health problems such as diabetes, heart disease, and cancer. The higher your number, the greater the risk.

If you are wondering, 'how much should I weigh?', your BMI can also show you what a healthy weight is for your height.


For a woman measuring 5' 6", a healthy score shows that she is in the normal range if she weighs betweens 115 lbs and 154 lbs.

How is BMI scored?

A person's score indicates if they are a healthy weight for their height, or if they are underweight, overweight or obese. There are some limitations to the formula, which we'll discuss later.

Your BMI is usually a two-digit number

It can range from 16 or under, to over 40. A low score of under 16 indicates that you are extremely underweight. Meanwhile, a score of over 40 shows that you have severe obesity.

What is a healthy BMI?

While a healthy weight depends on how tall you are, a healthy BMI is between 18.5 and 25.

How do I calculate my BMI?

There are two ways to calculate your BMI - with a BMI chart or with a calculator.

BMI Chart

The below chart shows weight along the left-hand column and height along the bottom bar. To find your score, you need to locate the point on the chart where your height and weight meet.

BMI Chart

BMI Calculator

It is very easy to calculate your BMI using our calculator. You just need to enter your age, gender, weight in pounds, and height in feet and inches.

The calculator then shows your BMI on the right and indicates which category you fall into. This can range from 'Underweight' to 'Extremely Obese'.


The calculator uses a formula developed by Adolphe Quetelet 150 years ago, which is as follows:

Metric BMI Formula: Weight (kg) / Height (m)2

As Quetelet was Belgian, he used metric units to devise the BMI formula. For this calculation, you need to divide your weight in kilograms with your height in meters squared.

For imperial measurements

This formula is a little more complicated.

Imperial BMI Formula: (Weight (lbs) x 703) / Height (inches)2

First, you need to multiply your weight in pounds by 703. You then divide this figure by your height in inches squared.

Are there limitations to BMI?

Although this method is a quick and effective body fat measurement, it does have limitations.

The formula is built on statistical averages, meaning any variance from what's considered "normal" can skew the results.


BMI tends to be overestimated in athletes and people with a muscular build.


A bodybuilder who measures 5'11" and weighs 190 lbs would be considered overweight with a BMI of 26.5.

This BMI suggests that this man has too much body fat. But, if he is very muscular, this is actually not the case. He only weighs more because he has more muscle mass, which is an indicator of a healthy body.


On the other hand, BMI may be underestimated in older people and those who have lost muscle.

How Can This Happen?

You can lose muscle if you lead a sedentary lifestyle, follow extreme diets, or do not consume enough protein. If your weight stays the same but your body is losing muscle, this means that your body fat percentage is higher than your BMI indicates.

When Does This Happen?

People often lose muscle as they get older and become less active. Seniors can often appear slim and score a healthy BMI. But, they may be carrying more fat mass than is healthy for their height.

To find out how much body fat you have, try our body fat calculator to see if you fall into the healthy range.

How is BMI used for children and teens?

For children aged two and over, the best assessment is using body mass index percentiles.

Girls and boys develop at different rates and have different body compositions depending on their age. So, a child's age and sex are also taken into consideration when measuring their BMI.

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