What Is BMI And How To Use BMI ?

The BMI, or body mass index, is an indicator of body size. It is measured by adding a person’s weight and height. The findings of a BMI measurement will show whether a person’s weight is sufficient for their height.

BMI is a test that can decide whether a person is underweight, has a healthy weight, is overweight, or is obese. A person’s health risks may increase dramatically if their BMI is outside of the healthy range.

Excess weight can lead to a number of health complications, including type 2 diabetes, high blood pressure, and cardiovascular issues.

Malnutrition, osteoporosis, and anemia may all be increased by a low weight. The doctor will make reasonable advice.

In adults, BMI does not specifically quantify body fat and does not take into account age, sex, race, or muscle mass.

It does, however, use traditional weight status categories to assist doctors in monitoring weight status through communities and recognizing possible conditions in individuals.

What Is The Formula For Calculating BMI ?

Both adults and children have the same BMI measurement. The following formulas are used in the calculation :


Formula and

Kilograms and
meters (or centimeters)

Formula: weight (kg) / [height (m)]2
The calculation for BMI in the metric system is weight in kilograms separated by height in meters squared. Since centimeters are widely used to measure height, multiply height in centimeters by 100 to get height in meters.
Example: Weight = 70 kg, Height = 180 cm (1.80 m)
Calculation: 70 ÷ [(1.80)x(1.80)] = 24.98

Pounds and

Formula: weight (lb) / [height (in)]2 x 703
Divide your weight in pounds (lbs) by your height in inches (in) squared and multiply by a conversion ratio of 703 to get your BMI.
Example: Weight = 160 lbs, Height = 5’6″ (66″)
Calculation: [160 ÷ [(66)x(66)]] x 703 = 24.96

How To Interpret BMI For Adults ?

BMI is interpreted using standard weight status categories for adults 20 years old and up. Men and women of all body types and ages fall into the same categories.

The following table shows the standard weight status categories for adults that correspond to BMI ranges.

BMIWeight Status
Below 18.5Underweight
18.5 – 24.9Normal or Healthy Weight
25.0 – 29.9Overweight
30.0 and AboveObese

How Accurate Is BMI Calculation ?

BMI considers natural variations in body shape to determine a healthy weight range for given height.

When determining if you’re a healthy weight, healthcare professionals may consider other factors in addition to your BMI.

Because muscle is much denser than fat, people who are extremely muscular, such as heavyweight boxers, weight trainers, and athletes, may be at a healthy weight despite having an obese BMI.

Your ethnic group can also influence your risk of developing certain diseases. Adults of Asian origin, for example, may have a higher risk of health problems if their BMI is less than 25.

If you’re pregnant, you shouldn’t use BMI as a metric. If you’re pregnant, seek advice from your midwife or doctor.

If you’re pregnant, you shouldn’t use BMI as a metric. If you’re worried about your weight, talk to your midwife or doctor.

How Do Doctors Use BMI ?

Although BMI is insufficiently accurate to be used as a diagnostic tool, it can be used to screen for potential weight problems in both adults and children.

A doctor or other healthcare professional may consider other factors if someone has a high or low BMI, such as :

  • Skinfold thickness measurements, which show how much fat is in adults and children’s bodies.
  • Dietary and physical activity assessments.
  • Talk about any family history of heart disease or other health issues.
  • Suggest additional health screenings if necessary.

Due to the results, the doctor or health professionals can make diet and exercise suggestions.

For Whom The BMI Calculator Is Not Useful ?

Muscle builders, long-distance runners, pregnant women, old people, and young children are not eligible for BMI. This is due to the fact that BMI does not consider whether the weight is carried as muscle or fat, only the number. Those with more muscle mass, such as athletes, may have a higher BMI but are not at greater risk of developing health problems. A lower BMI is associated with those who have less muscle mass, like children who have not finished their growth or old people who may be losing muscle mass. Because a woman’s body composition changes throughout pregnancy and lactation, BMI is ineffective.

BMI Calculation For Children And Teenagers

BMI is not related to age in adults and is the same for both sexes.

BMI calculation in children and teenagers, on the other hand, is a little different. At various ages, girls and boys mature at various rates and have various levels of body fat. As a result, BMI estimates during childhood and adolescence take age and gender into account.

Doctors and other health practitioners do not classify children into safe weight groups for the following reasons :

  • They grow with each passing month.
  • Body shapes change at different rates in men and women.
  • As the child grows higher, they change.

For children and teenagers BMI is measured in the same way as adults’ BMI is calculated: by calculating height and weight. The BMI number and the person’s age are then inserted into a sex-specific BMI-for-age table. This will demonstrate whether the child’s weight is within a reasonable range.

What Other Methods Are There For Assessing Body Fat Besides The BMI ?

Skinfold thickness measurements (with calipers), dual-energy x-ray absorptiometry (DXA), bioelectrical impedance, underwater measuring and isotope dilution are several of the other methods for assessing body fatness. These techniques, however, are not always readily accessible, and they are either costly or require the use of highly skilled staff. Furthermore, many of these approaches can be difficult to standardize through observers or machines, rendering cross-study and time-period comparisons more difficult.

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