BMI Calculator

Calculate your BMI
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Step 1: Basic Information
Step 2: Daily Activities *(Optional)
Step 3: Select your goal *(Optional)
Basal Metabolic Rate (BMR):
Body Mass Index (BMI):
Target calorie/per day:
Macronutrient Balance:
Fat: 0 g
Protein: 0 g
Carb: 0 g

Body Mass Index Calculator Chart

Use the BMI chart to determine your BMI rating. The table shows the World Health Organization BMI classification system. The rating scale is the same for male and female.

Body Mass IndexStatus
Below 18.5Underweight
18.5–24.9Normal weight
30.0–34.9Obesity class I
35.0–39.9Obesity class II
Above 40Obesity class III

BMI – The Body Mass Index

The WHO defines the body mass index as “a value derived from the mass and height of a person.” The BMI is the body mass divided by the square of the body height and is expressed in units of kg/m2, resulting from mass in kilograms and height in meters.


WHO and the Categorization of BMIs into Quartiles

In 1993, the WHO assembled an Expert Consultation Group with the aim of developing a uniform classification of the BMI. The results, published in 1995, are valid to this date. Four discrete categories were established: underweight, normal, overweight, and obese.


Graphical representation of BMI

The 4 categorical ranges for BMI can be plotted against their respective criteria (height and mass measurements) for ease of understanding. Exact values can be inferred through such a curve.

Bmi Calculator Chart


Why is BMI used?

BMI Calculator is an immediate, one step evaluation and non-invasive assessment of body fat. In comparison with other approaches, BMI is based purely on height and weight, and anyone with access to the appropriate equipment can have their BMI tested and calculated on a routine basis with reasonable accuracy. The body mass index is still the parameter-of-choice for defining anthropometric height/weight characteristics in adults.


Importance of BMI

For both adults and children, BMI Calculator is a reliable indication of body fat. BMI should be used to assess population weight status and as a screening tool to identify prospective weight concerns in individuals.

It is not the only risk identification tool out there but it offers easier application and can be a great start in assessing risk.

If you’re on your goal-weight journey, your BMI will help you understand the energy you need to burn, the most appropriate weight loss goal and the number of calories you need to consume to lose weight and vice versa.


Advantages of BMI

  1. Assessment of Health

A patient’s BMI is used by medics as a biometric marker of their overall health. The likelihood of a person developing chronic illnesses such as heart disease, hypertension or diabetes relies greatly on his/her healthy BMI.

  1. Guiding Your Personal Health Goals

It is essential for you to know your BMI when you’re thinking about setting yourself up for health and fitness. For example, if you have a BMI of 15, you have to work on weight-gain strategies in order to be healthier. The best route for you to take at this point is to add a caloric surplus of around 3-500 calories per day to put on around 3-4lbs per month until you get your BMI into the healthy range. Similarly, if your BMI is 31, for example, you will be categorized as overweight. Your priority in this case is to lose weight. A caloric surplus of 500-1000 per day, alongside a few weekly trips to the gym, will help you to lose between 4-10 pounds per month, until you come down to a healthier BMI range.

  1. It is Objective

BMI may not be the most accurate measurement because it does not take into account muscle mass or any extra factors that may contribute to abnormal body weight. However, it is objective. You can see the results based on facts and figures. BMI will not sugar-coat things for you.

However, always remember that if your BMI is outside a healthy range, there is likely more to the story than is apparent.


A Peek into the Past

This standardized formula was created by a Belgian mathematician. In the 1830s, Lambert Adolphe Jacques Quetelet set out to find the “l’homme moyen” or the “average man“. His study provided the law of averages to physicists that came after. One can take thousands of measurements, compare them, and find the ideal weight. Through calculating these samples it was found that weight typically increases in relation to the square height of a person.

One major limitation to Quetelet’s experiment was that all the participants were western European men. The experiment could not, however, measure individual health.


Interesting Myths & Facts about BMI

  • Myth: A low BMI means you are healthy.
  • Fact: A low BMI in a pregnant woman is a huge health risk. So this statement is not consistent with exceptions.
  • Myth: A high BMI increases the risk of a heart attack.
  • Fact: It is true. Higher BMI/ obesity can lead to a higher risk of cardiovascular diseases.
  • Myth: Eating healthy and exercising means you’ll have a low BMI.
  • Fact: BMI is defined by a range and not at all a discrete value.
  • Myth: You are healthy if your BMI is between 19 and 25.
  • Fact: Almost always true.
  • Myth: The BMI is an excellent measure of health.
  • Fact: It is an estimate and not an absolute clinical finding.


BMI for Health Risk Detection

Knowing your BMI can help you and your GP determine any health risks you may face if it’s outside of the healthy range.

Being overweight can lead to a range of chronic conditions including:

  • Type 2 Diabetes
  • High blood pressure
  • Heart or blood vessel problems
  • Cardiovascular disease
  • Musculoskeletal problems

Being underweight, on the other hand, can result in other health issues like:

  • Risk of malnutrition
  • Osteoporosis
  • Anemia


Points to Consider

Things to remember when calculating BMI for an adult

As handy as it is, we have to consider exceptions as it happens with all other tests. BMI is a measure of extra weight rather than excess body fat; so, it sometimes serves as a substitute for body fatness.

  • On average, older persons have more body fat than younger ones with a similar BMI.
  • On average, women have more total body fat than men with a comparable BMI.

Things to remember when calculating BMI for children

The difficulties in using BMI calculations also apply to children and adolescents. Other variables, such as height also affect the link between BMI and body fat in children.

Additionally, the accuracy of BMI varies significantly depending to the degree of body fat in children individually.


When should I worry about my BMI?

If your BMI is 18.5 to 24.9, it falls within the normal or “healthy weight” range. If your BMI is 25.0 to 29.9, it falls within the “overweight range”. If your BMI is 30.0 or higher, it falls within the “obese range”.


Potential limitations of BMI

Consider the examples of four different people, all the same height and weight with a BMI of 26 — technically overweight, according to the index:

  1. One is a 75-year-old man
  2. One is a bodybuilder
  3. One is a pregnant woman
  4. One is sedentary teenager

The pregnant woman tips the scales because she’s carrying another human. The bodybuilder goes over the limit because of his muscle mass and bone density, which weigh more than fat. The elderly man crosses the line because fat accumulates as people age. The teen may have some weight-related health concerns.

Age, gender, ethnic origin, and muscle mass all affect the link between BMI and body fat. BMI makes no distinction between excess fat, muscle, or bone mass, and does not indicate how fat is distributed among individuals. BMI does not distinguish between body fat and lean body mass. Other measures of body fat, such as skinfold thickness may be more accurate than BMI, according to some studies.

The waist circumference (sometimes divided by height) is another easy way to assess fat distribution and is nowadays a trusted source of measurement.


What If my BMI is Abnormal?

Our understanding of obesity-related health hazards is based on the relationship of BMI to other health outcomes. There are few reference standards for body fatness based on the above-mentioned metrics, and without established risk categories, determining whether an individual’s body fatness is low, moderate, or high is often challenging.

In any case, abnormal BMI may or may not be associated with any potential risks. A person can be completely healthy and still have an abnormal value for BMI. Similarly, you can be underweight according to your BMI and still be perfectly healthy. Instead of assuming anything, one should take advice from a general practitioner or a nutritionist before taking further measures to improve his/her overall health.

Body Mass Index (BMI)

The Body Mass Index, commonly referred to as BMI, is a tool used worldwide to categorize an individual's body weight in relation to their height. It offers a numerical representation of a person's weight status, offering insight into potential health risks associated with being underweight, normal weight, overweight, or obese.

Table of Contents

History of BMI

The history of BMI is quite fascinating. It dates back to the 19th century when a Belgian mathematician named Adolphe Quetelet introduced the Quetelet Index. This index was the early form of what we now know as BMI. Quetelet was attempting to define the "average man" using statistical measures, and in his endeavors, he stumbled upon this index. The term "Body Mass Index" was later coined in the 20th century and became the standard term used by clinicians and researchers.

How is BMI Calculated?

Calculating BMI is relatively straightforward. Here's the formula:

BMI = weight (kg) / [height (m)]^2

For those using the imperial system, the formula is:

BMI = [weight (lbs) / [height (in)]^2] * 703

Understanding BMI Categories

The World Health Organization (WHO) has defined specific categories based on BMI values to help identify potential health risks. These categories are:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI between 18.5 and 24.9
  • Overweight: BMI between 25 and 29.9
  • Obese Class I: BMI between 30 and 34.9
  • Obese Class II: BMI between 35 and 39.9
  • Obese Class III: BMI 40 or higher

Implications of Different BMI Values

BMI is not just a number; it is a window into a person's potential health risks. Here are some implications associated with different BMI categories:

  • Underweight: Being underweight can be associated with malnutrition, osteoporosis, and a weakened immune system. It can also be indicative of underlying health problems.
  • Normal weight: This range is associated with a lower risk of cardiovascular diseases and other chronic conditions.
  • Overweight and Obesity: These categories are linked with a higher risk of heart diseases, diabetes, certain cancers, and more. The risks increase with the progression from overweight to obese classifications.

Limitations of BMI

While BMI offers a quick way to categorize individuals based on their weight, it is not without flaws. Some limitations include:

  • Does not differentiate between muscle and fat. Therefore, bodybuilders or athletes might be categorized as overweight or obese when they have a lower body fat percentage.
  • It doesn't account for distribution of fat. Abdominal fat, for example, poses more health risks than fat stored in other areas of the body.
  • It doesn't consider age, gender, or bone structure, all of which can influence body composition.

BMI in Different Populations

BMI values and implications can vary across different populations. Ethnicity, genetic makeup, and cultural factors play a role in body composition. For example:

  • Asian populations tend to have a higher body fat percentage at lower BMI values.
  • African populations might have a lower risk of certain health conditions at higher BMI values compared to other populations.

Factors Affecting BMI

BMI can be influenced by various factors. Some of these include:

  • Diet: Overconsumption of high-calorie foods can lead to weight gain.
  • Physical Activity: Sedentary lifestyles contribute to an increase in BMI.
  • Genetics: Genetic makeup can influence how the body stores fat.
  • Metabolism: Metabolic rates determine how the body uses energy.
  • Health Conditions: Some conditions, like hypothyroidism, can influence weight and BMI.

Improving and Maintaining a Healthy BMI

Improving BMI revolves around adopting a balanced lifestyle. Recommendations include:

  • Eating a balanced diet with plenty of fruits, vegetables, and whole grains.
  • Engaging in regular physical activity.
  • Limiting intake of sugars, salts, and saturated fats.
  • Monitoring weight and making adjustments to lifestyle as needed.


BMI is a valuable tool, but it's essential to understand its limitations and nuances. Using resources like the BMI calculator on is a great starting point, but always refer to healthcare professionals for comprehensive health assessments.