BMI Calculator

It helps you calculate your body mass index (BMI). BMI is a measure of body fat based on height and weight that is used to predict the risk of developing obesity-related health problems, set weight loss goals, monitor your weight loss progress.

BMI calculator


Your BMI is......

less than 18.5: Underweight
18.5 - 24.9:Normal weight
25 - 29.9:Overweight
30 - 34.9:Class I Obese
35 - 39.9:Class II Obese
40 upwards:Class III Obese

Introduction to BMI

The Body Mass Index (BMI) is a measurement of a person’s leanness or corpulence based on their height and weight, and it is used to quantify tissue mass. It is commonly used to determine whether a person has a healthy body weight for their height. Specifically, the BMI calculation result is used to determine whether a person is underweight, normal weight, overweight, or obese based on where the value falls within a given range. These BMI ranges vary by region and age and are sometimes further subdivided into subcategories such as severely underweight or severely obese. Being overweight or underweight can have serious health consequences, so while BMI is an imperfect measure of healthy body weight, it can help determine whether additional testing or action is needed. The table below shows the different BMI-based categories that the calculator uses.

Adult BMI Table

This is the World Health Organization’s (WHO) recommended body weight for adults based on BMI values. It is appropriate for both men and women over the age of 18.

BMI range – kg/m2
Severe Thinness< 16
Moderate Thinness16 – 17
Mild Thinness17 – 18.5
Normal18.5 – 25
Overweight25 – 30
Obese Class I30 – 35
Obese Class II35 – 40

Obese Class III

40″}”>> 40

BMI Table for Children and Adolescents Aged 2 to 20

BMI classification is recommended by the Centers for Disease Control and Prevention (CDC) for children and adolescents aged 2 to 20.

Percentile Range
Healthy weight5% – 85%
At risk of overweight85% – 95%

The Risks of Being Overweight

If you are overweight, you are at a greater risk for developing serious diseases and health conditions. The Centers for Disease Control and Prevention (CDC) have listed some of these risks below.

  • Blood pressure is high.
  • Higher LDL cholesterol levels, which are widely considered “bad cholesterol,” lower HDL cholesterol levels, which are considered “good cholesterol in moderation,” and high triglyceride levels.
  • Diabetes type II.
  • Coronary artery disease.
  • Stroke
  • Gallbladder dysfunction.
  • Osteoarthritis is a type of joint disease caused by cartilage breakdown.
  • Sleep apnea and breathing difficulties.
  • Certain types of cancer (endometrial, breast, colon, kidney, gallbladder, liver)
    Life quality is poor.
  • Clinical depression, anxiety, and other mental illnesses.
  • Body aches and difficulties performing certain physical functions.
  • In general, a higher risk of death when compared to those with a healthy BMI.

As you can see from the list in the previous paragraph, being overweight can have a variety of negative, and in some cases fatal, consequences. In general, a person should try to keep their BMI below 25 kg/m2, but they should also consult their doctor to see if they need to make any changes to their lifestyle to be healthier.

The Risks of Being Underweight

Being underweight has its own set of risks, which are listed below:

  • Anemia, malnutrition, and vitamin deficiencies (lowered ability to carry blood vessels)
  • Osteoporosis is a disease that causes bone weakness, increasing the likelihood of a bone fracture.
  • A reduction in immune function
  • Problems with growth and development, particularly in children and teenagers
  • Women may experience reproductive problems as a result of hormonal imbalances that disrupt the menstrual cycle. Women who are underweight are also more likely to miscarry during the first trimester.
  • Complications that may arise as a result of surgery.
  • In general, a higher risk of death when compared to those with a healthy BMI.

Underweight can be a symptom of an underlying condition or disease, such as anorexia nervosa, which has its own set of risks. Consult your doctor if you believe you or someone you know is underweight, especially if the cause does not appear obvious.

BMI’s Limitations

Although BMI is a useful measure of healthy body weight, it has its limitations. It does not take into account body composition. Different people have different body types, with different amounts of muscle, bone mass and fat. BMI should therefore be considered alongside other measurements, and not used on its own.

In adults:

BMI is not an accurate measure of healthy weight because it only takes into account excess body weight, not excess body fat. BMI is also affected by factors such as age, sex, ethnicity, muscle mass, and activity level. For example, an older person who is considered a healthy weight, but is not active, may have excess body fat even though they are not heavy. This would be considered unhealthy, while a younger person with more muscle mass of the same BMI would be considered healthy. In athletes, particularly bodybuilders, who would be considered overweight due to muscle mass, they may actually be at a healthy weight for their body composition. Generally, according to the CDC:

  • Older adults have more body fat than younger adults with the same BMI.
  • For the same BMI, women have more body fat than men.
  • Muscular people and highly trained athletes may have higher BMIs due to their large muscle mass.

In children and adolescents:

There are some limitations to using BMI to measure body fat in children and adolescents. For example, height and sexual maturation can impact BMI and body fat levels in kids. Additionally, BMI is a more accurate measure of excess body fat for obese children than it is for overweight children. This is because BMI in overweight children could be due to increased levels of either fat or fatfree mass (anything except for fat, including water, organs, muscle, etc.). In thin children, the difference in BMI might also be attributable to fatfree mass. Even with these limitations, BMI is still a fairly accurate measure of body fat for the majority of the population. As such, it can be effectively used in conjunction with other measures to help determine an individual‘s healthy body weight.

BMI Formula

SI, Metric Units:

BMI=mass (kg)/height2 (m)=72.57/1.782= 22.90kg/m2

1 rep max
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