How the BMI is Calculated

How The BMI is Calculated? BMI is short for Body Mass index. Calculating BMI is one of the tasks most people out there find hard or don’t know how to calculate.

If you are eager to know how to calculate body mass index, with this very content you will learn how, just make sure you read to the end.

Table of Contents

The Body mass index is simply someone’s weight in kilograms shared by the square of height in meters. The BMI is an inexpensive and easy screening method for weight categories such as underweight, healthy weight, overweight, and obesity. Body Mass Index does not measure body fat directly, but it is moderately correlated with more direct measures of body fat 1,2,3.

However, BMI seems to be as strongly correlated with various metabolic and disease outcomes as are these more direct measures of body fatness 4,5,6,7,8,9.

How BMI is calculated?

BMI is calculated the same way for both adults and children. The calculation is based on the following formulas;

Kilograms and meters (or centimeters) Formula: weight (kg) / [height (m)]2

Using the metric system, the formula for BMI is weight in kilograms divided by height in meters squared. This height is commonly measured in centimetres, divide height in centimetres by 100 to obtain height in meters.

For Instance: Weight = 68 kg, Height = 165 cm (1.65 m)

Calculation: 68 ÷ (1.65)2 = 24.98

Pounds and inches Formula: weight (lb) / [height (in)]2 x 703

Calculate the BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703.

For Instance: Weight = 150 lbs, Height = 5’5″ (65″)

Calculation: [150 ÷ (65)2] x 703 = 24.96

How BMI is interpreted for Adults

For adults 20 years old and above, BMI is interpreted using standard weight status categories. These categories are the same for men and women of all body types and ages.

However, the standard weight status categories associated with BMI ranges for adults are shown in below.

Below 18.5 Underweight
5 – 24.9 Healthy Weight
0 – 29.9 Overweight
0 and Above Obesity

For children and teens, the interpretation of BMI depends upon age and sex.

Is BMI interpreted the same way for children and teens as it is for adults?

BMI is interpreted differently for children and teens, although it is calculated using the same formula as adult BMI. Children’s and teens’ BMI need to be interpreted based on age and sex because the amount of body fat changes with age and the amount of body fat differs between girls and boys.

Further, the CDC BMI-for-age growth charts take into account these differences and visually display BMI as a percentile ranking. These percentiles were gotten using representative data of the US population of 2- to 19-year-olds that was collected in various surveys from 1963-65 to 1988-9411.

However, Obesity among 2 to 19 years olds is defined as a BMI at or above the 95^th percentile of children of the same age and sex in this 1963 to 1994 reference population. Take for instance, a 10-year-old boy of average height (56 inches) who weighs 102 pounds would have a BMI of 22.9 kg/m2. This would place the boy in the 95^th percentile for BMI – which means that his BMI is greater than that of 95% of similarly aged boys in this reference population – and he would be considered to have obesity.

How Good is BMI as an Indicator of Body Ftness?

The correlation between BMI and body fatness is fairly strong, but even if 2 persons have the same BMI, their level of body fatness may differ. On a general note, at the same BMI;

Older persons, on average, tend to have more body fat than younger adults.
Athletes have less body fat than non-athletes.
Women tend to have more body fat than men.
The amount of body fat may be higher or lower depending on the racial/ethnic group.

The accuracy of BMI as an indicator of body fatness also seems to be higher in persons with higher levels of BMI and body fatness. While, a person with a very high BMI (e.g., 35 kg/m2) is likely to have high body fat. And a relatively high BMI can be a result of either high body fat or high lean body mass (muscle and bone).

How do I Calculate my BMI formula?

The formula is: BMI = kg/m2 where kg is a person’s weight in kilograms and m2 is their height in metres squared. A BMI of 25.0 or above is overweight, while the healthy range is 18.5 to 24.9.

What is BMI & How is it Calculated?

BMI is short for Body Mass Index. BMI is a person’s weight in kilograms (or pounds) divided by the square of height in meters (or feet). A high BMI can show high body fatness

What are the Health Consequences of Obesity for Adults?

People who have obesity are at increased risk for many diseases and health conditions, including the following:

Coronary heart disease
Stroke
Gallbladder disease
Osteoarthritis (a breakdown of cartilage and bone within a joint)
All causes of death (mortality)
High blood pressure (hypertension)
High LDL cholesterol, low HDL cholesterol, or high levels of triglycerides (dyslipidemia)
Type 2 diabetes
Mental illnesses such as clinical depression, anxiety, and other mental disorders
Body pain and difficulty with physical functioning
Sleep apnea and breathing problems
Chronic inflammation and increased oxidative stress
Some cancers (endometrial, breast, colon, kidney, gallbladder, and liver)
Low quality of life