BMI Calculator

161718.525303540UnderweightNormalOverweightObesityBMI = 23.15

BMI categories table

BMI CategoryBMI Range (kg/m^2)Health Risk
Severe ThinnessLess than 16.0Very high
Moderate Thinness16.0 - 16.9High
Mild Thinness17.0 - 18.4Mild
Normal range18.5 - 24.9Low
Pre-obese (Overweight)25.0 - 29.9Increased
Obese Class I (Moderate)30.0 - 34.9Moderate
Obese Class II (Severe)35.0 - 39.9Severe
Obese Class III (Very Severe)40.0 or moreVery Severe (High risk of comorbidities)

BMI chart

BMI chart
Source: wikimedia

What is BMI?

Body Mass Index (BMI) is a numerical value of a person's weight in relation to their height. It is a widely used screening tool to categorize individuals into various weight categories, which may indicate their level of body fat and potential health risks.

Here's how BMI is defined and used:


BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. The formula for BMI is:

BMI(kg/m2) =

In imperial units, the formula is modified to:

BMI(kg/m2) =
× 703


BMI values are used to define various weight status categories, such as underweight, normal weight, overweight, and obesity. These categories can provide a quick indication of whether an individual might be at risk for health problems related to their weight.


While BMI is a useful quick screening tool, it has limitations. It does not directly measure body fat, and it does not account for the distribution of fat, muscle, bone mass, overall body composition, or racial and sex differences. Therefore, individuals with a high muscle mass (like athletes) may be categorized as overweight or obese when they are actually healthy.

Use in Healthcare:

Healthcare professionals use BMI along with other assessments, such as skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings to make informed decisions about an individual's health risks and to recommend interventions.

BMI is not a diagnostic tool on its own. A high or low BMI may indicate the need for further, more direct assessments of body composition and health risk.

Risks associated with being overweight

Being overweight, usually defined as having a Body Mass Index (BMI) over 25. BMI is a widely used measure to categorize weight status and is calculated by dividing a person's weight in kilograms by the square of their height in meters. While BMI does not measure body fat directly, it correlates with direct measures of body fat and can be a quick screening tool to identify potential weight problems in adults.

However, it's important to note that BMI does not differentiate between muscle and fat mass, does not take into account the distribution of fat, and may not be accurate for all ethnic groups, athletes, or older individuals.

Here are risks associated with being overweight as determined by a higher BMI:

  • Cardiovascular Diseases
  • Type 2 Diabete
  • Metabolic Syndrome
  • Sleep Apnea
  • Cancers
  • Gallbladder Disease
  • Fatty Liver Disease
  • Reproductive Problems
  • Psychological Effects
  • Reduced Quality of Life
  • Increased Inflammation

Risks associated with being overweight

Being underweight, typically defined as having a Body Mass Index (BMI) below 18.5, can be just as harmful to your health as being overweight. Here are some of the health risks associated with being underweight:

  • Nutritional Deficiencies
  • Immune System Impairment
  • Osteoporosis
  • Growth and Development Issues
  • Fertility Issues
  • Muscle Wasting
  • Increased Risk of Surgical Complications
  • Heart Problems
  • Pregnancy Risks
  • Hair Loss
  • Skin Issues
  • Feeling Cold

While BMI is a useful indicator of potential health risks, it should be used as part of a broader assessment that includes other health indicators, family history, diet, physical activity, and other factors. Health professionals often use additional measurements, such as waist circumference, to evaluate health risks. It is always recommended to consult with a healthcare provider for a full evaluation and personalized advice.

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