Body Mass Index (BMI)


In the early 20th century, after modern advances allowed us to better understand the negative effects of obesity on health and mortality, the insurance companies and the medical community struggled to come up with a way to measure a person’s level of body fat.

Inventions such as the use of calipers to measure the thickness of the skin in order to determine body fat percentage have provided the medical community a more accurate way to assess body fat percentage.

It is nearly impossible to gather data on body fat for an entire population of people. Gender, height, and weight are readily available, however, formulas to determine obesity percentage among a larger group of people using the data available are less accurate. The BMI formula does not take into account the differences in muscle mass or bone density, so for a percentage of the population, it may not be a good tool to use for determining the level of body fat.

BMI Calculator – Body Mass Index

BMI ranges

There are five basic ranges within the BMI scale:

  • Underweight = less than 18.5
  • Normal weight = 18.5 – 24.9
  • Overweight = 25 – 29.9
  • Obesity = 30 – 35
  • Severe obesity = 35 and more

The BMI Prime is a nifty modification to our own BMI calculator. It’s a decimal number where 1.0 = the upper limit to the “normal BMI” range. It’s a super easy way to see if you’re overweight or not. If your BMI Prime is more than 1, then you’ve got some weight to lose.