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BMI Calculator
Calculate Your Body Mass Index for Free

The term body mass index (BMI) is often used by people without fully understanding what it means and how it can be helpful.

While calculating BMI is very simple, especially with the free BMI calculator on this page, it’s best to take a step back so that you know what to do with BMI.

BMI Calculator

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Made by: Total Shape

What Do Your Results Mean?

The calculated body mass index (BMI) value will let you know how much of your body composition is made up of fat, and that there are healthy BMI ranges that you should be aiming for. What’s important to note is that you should not be aiming for the lowest possible BMI results.Your body needs a certain amount of body fat to function properly, and generally speaking, you should be aiming for a BMI value right around 20. Being significantly above or below this BMI is an indication that you need to make changes to your weight status and lifestyle. Or in other words, decrease body fat percentage or slightly increase it.If you don’t take action, constantly high BMI can lead to some serious health conditions.In the following table, you can see what your calculated BMI result is saying about your body composition based on the BMI calculator.

What Is Body Mass Index (BMI)?

BMI is a way for you to calculate the ratio of your height and weight to get a value that indicates roughly what percent of your body is fat. Generally speaking, the higher your tissue mass value is, the more likely you are to be overweight or obese, thus more prone to health problems such as high blood pressure, heart disease, or sometimes even type 2 diabetes.The caveat to this is that if you’re a serious bodybuilder, then the results of body mass index calculation could mean you’re obese even though you might have minimum amounts of body fat. However, for the average person that wants to get to a healthy weight with less flabby stuff, calculating your body mass index is a really good way to measure your progress.

Either way, talking to your dietitian or general healthcare provider could help you make the most out of your BMI.So, let’s take a look at how BMI works.

How Is BMI Calculated?

The BMI calculator is quite simple to use and won’t take a maths degree or scientific calculator to work out. The first thing you need to calculate body mass index do is to measure your height and weight first thing in the morning before eating and drinking. Keep a note of the two values.If you’re working in metric values, then you can use the following formula to calculate the BMI value yourself:

BMI = weight (kg) ÷ height^2 (m^2) 

If you’re taking imperial measures, then use this formula to calculate BMI:

BMI = weight (lb) ÷ height^2 (in^2) × 703

To make it even easier, just plug your measures into the BMI calculator on this page, and you’ll have an immediate result.

BMI Table For Adults

According to World Health Organization (WHO), this are the body weight categories based on BMI values for adults. It’s applied for both women and men, age 18 or older.


BMI Category

Below 15

Very severely underweight

15 to 16

Severely underweight

17 to 18.5


18.6 to 25

Healthy weight

26 to 30


31 to 35


36 to 40

Severely obese

Over 40

Very severely obese

BMI Table For Children And Teens

When calculating BMI value for children and teenagers, you also need to take consider the fact that male and female height and weight dramatically change during the early years of their lives. This is why you also have to use their age and gender when calculating BMI. 

BMI for children and teens is expressed as a percentile compared to other children of the same age and gender.

Percentile Range

BMI Category



5% to 85%

Normal or Healthy Weight

85% to 95%




Dangers related to being overweight or obese

According to the Centers for Disease Control and Prevention (CDC), being overweight is the leading cause of many dangerous diseases and health conditions. This is very important information for adults to remember, considering the increasing number of children and teens facing severe weight problems in last 2 decades.

The list of potential health problems is long and intimidating:

  • Stroke
  • Type 2 diabetes
  • Coronary heart disease
  • Hypertension (elevated blood pressure)
  • Higher levels of LDL cholesterol, which is generally considered “bad cholesterol”
  • Lower levels of HDL cholesterol, which is in moderation considered “good cholesterol”
  • High levels of triglycerides
  • Gallbladder disease
  • Osteoarthritis (joint illness)
  • Sleep apnea and breathing issues
  • Cancers (kidney, liver, colon, gallbladder, breast, endometrial)
  • Reduced quality of life
  • Mental disturbances and illnesses (anxiety, panic attacks, depression, etc.)
  • Statistically higher risk of mortality compared to those with healthy BMI value

Adults striving to be healthier should try to reduce their body mass index below the 25kg/mmark. The easiest way to get there is by reducing calorie intake, which will reduce your overall body fat percentage and put you in the optimal BMI range.

Consulting your doctor for medical advice on how to maintain a normal weight is always a good idea if you notice your body fat is hard to control or if you have existing health risks.

Limitations of BMI

Despite the fact that BMI is commonly used as a good indicator of healthy body weight, it does have some drawbacks, unfortunately.

BMI is often considered only as a rough estimate that doesn’t provide a full picture of a person’s health. Since the only information needed for BMI calculator is your height and weight, you can start to understand why BMI is taken only as an estimation – a BMI calculator can’t take your body type and body composition into consideration.

The same rules can’t be applied to everyone due to different distributions of bone, muscle mass and fat. For example, individuals who carry a lot of muscles will have a high BMI because the percentage of their muscle weight is higher than the percentage of their fat weight.

The good news is that not everyone is a bodybuilder with huge amounts of pure muscle mass and almost no body fat. This is why on the bottom line, BMI can be used as a good enough estimate of body weight for the vast majority of people.

So if you haven’t already, quickly plug your height and weight into our BMI calculator to determine whether or not you’re in a healthy weight range. Your BMI may surprise you!

And don’t forget to talk to your healthcare provider or dietitian to make sure you take advantage of your BMI calculator results.