How to calculate BMI plus healthy lifestyle and weight

How can you calculate your BMI?

Where can you find out how to measure and calculate your BMI — and how does it relate to whether or not you’re overweight?


BMI, or Body Mass Index, is a measure of body fat based on your height and weight for adults. The calculation is based on the following equation:

Weight (in pounds) ÷ Height (in inches)² x 703

If that does not compute, here’s the English language version:

  • Multiply your weight in pounds by 703
  • Divide the result by your height in inches
  • Divide that result by your height in inches again

Then you take that number and figure out your score. These are the scoring descriptions and the terms used by the National Library of Medicine:

Below 18.5 Underweight
18.5 to 24.9 Healthy
25.0 to 29.9 Overweight
30.0 to 39.9 Obese
Over 40 Extreme or high risk obesity

For a quick and easy BMI calculation, try this NIH calculator tool, or this one from Harvard (which also has a simple chart). Enter your height and weight, and the calculator will make an educated estimate based on your inputs.


Now, BMI does have some limitations — a lot of limitations, in some cases. If you have a muscular or athletic build, for example, it may overestimate fat. In older people and in those who have lost muscle mass, it may underestimate. (Find out more about BMI calculations here.)

MORE: Women: Do you have the ideal figure? Here’s what ‘they’ thought in 1950

The most accurate method of determining your body fat percentage is asking your healthcare provider — or even a certified personal trainer — to measure you, which will either be done via calipers or water displacement.

In any case, BMI is only one factor to look at in maintaining a healthy lifestyle — but it can certainly act as a benchmark for comparison and improvement.

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