What Is the Body Mass Index (BMI)?

Medically Reviewed on 10/18/2021

What is the body mass index (BMI)?

Body mass index (BMI) is an approximate measure of obesity.
Body mass index (BMI) is an approximate measure of obesity. Here is how to calculate BMI and determine your ideal weight.

Body mass index (BMI) is a person’s weight in kilograms divided by the square of the body’s height in meters. It indicates whether the weight is appropriate for the person’s height. Another way to calculate BMI is to multiply the person’s weight in pounds by 703 and divide it by the height (in inches) squared.

BMI is the most inexpensive screening tool to measure obesity. Although it does not directly measure body fat, it can be correlated with more direct measures of body fat.

The various categories of BMI include the following

  • BMI values of less than 18.5 kg/m2 are considered underweight.
  • BMI values between 18.5 kg/m2 to 24.9 kg/m2 are healthy.
  • BMI values between 25 kg/m2 to 30 kg/m2 are overweight.
  • BMI values greater than 40 kg/m2 are considered obese.

Example: If a person weighs 68 kg and is 165 cm (1.65 m) tall, BMI is calculated as 68 ÷ (1.65)2 = 24.98 kg/m2, which means that the person has a BMI of 24.98 and is considered to be a healthy weight.

How is BMI used?

Body mass index (BMI) is a screening tool. It does not reflect body fat or the health status of an individual. Moreover, the physician will also assess the individual’s diet, physical activity, and family history to determine if BMI is a health risk.

BMI Calculator

To use this calculator:

  1. The default BMI of 16.6 shown on the tool is for a 5'5" person who weighs 100 lbs.
  2. Use the switch on top to pick either metric or imperial measurements.
  3. Set the height and weight dials to match your height and weight.
  4. View your BMI number at the center of the tool and see where you fall on the obesity chart.

BMI values are based on clinical data about averages for these measurements across a wide swath of people.

The body mass index (BMI) is used to assess your weight relative to your height. This BMI calculator allows you to easily screen yourself for obesity or extra, unhealthy weight. If your results from the calculator aren't in the healthy range, don't worry too much. People with muscular builds may be classified as obese, even with a low body fat percentage and optimum health, simply because the BMI formula uses only two data points.

What are the BMI trends for adults in the United States?

  • Since the 1970s, the prevalence of adult body mass index (BMI) above 30 kg/m2 has been increasing.
  • Although recently, there is a decline in this trend except for older women 
  • Women over the age of 60 years old have continued to remain obese all these years.

Are there any issues with using BMI?

Healthcare professionals often use body mass index (BMI) as a screening tool to identify weight problems. Although it gives a good estimation of body fat for most individuals, it may be erroneous to use in the case of bodybuilders and other muscular people who have high muscle mass.

High bone density may also result in high BMI. BMI may underestimate body fat in people who have lost muscle mass, especially in the older population. At the same BMI, body fatness may differ among the following populations:

  • Men and women
  • Blacks and whites
  • Older people and younger adults
  • Athletes and non-athletes

What is the ideal weight?

The ideal weight has been mentioned in the below table

Ideal weight by height chart
Height Minimal Risk (BMI under 25) Moderate Risk (BMI 25-29.9) Overweight High Risk (BMI 30 and above) Obese
4'10'' 118 lbs or less 119-142 lbs.  143 lbs. or more
4'11'' 123 or less 124-147  148 or more
5'0'' 127 or less 128-152  153 or more
5'1'' 131 or less 132-157 158 or more
5'2'' 135 or less 136-163  164 or more
5'3'' 140 or less 141-168 169 or more
5'4'' 144 or less  145-173 174 or more
5'5'' 149 or less 150-179  180 or more
5'6'' 154 or less 155-185 186 or more
5'7'' 158 or less 159-190 191 or more
5'8'' 163 or less 169-202 197 or more
5'9'' 168 or less 169-202 203 or more
5'10'' 173 or less 174-208 209 or more
5'11'' 178 or less 179-214 215 or more
6'0'' 183 or less 184-220 221 or more
6'1'' 188 or less 189-226 227 or more
6'2'' 193 or less 194-232 233 or more
6'3'' 199 or less 200-239 240 or more
6'4'' 204 or less 205-245 246 or more

What are the advantages of maintaining a healthy weight?

By maintaining a healthy weight, an individual enjoys the following advantages


The Best Diet Tips: How to Lose Weight the Healthy Way See Slideshow
Medically Reviewed on 10/18/2021
Medscape Medical Reference

American Heart Association https://www.heart.org/en/healthy-living/healthy-eating/losing-weight/bmi-in-adults

CDC https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html#Consequences