Body Mass Index (BMI)

The body mass index (BMI) is an equation for working out your human body fat based on your weight and height. Although not entirely accurate it does give you a very good understanding of where you sitting in terms of a healthy weight. Body mass index is defined as the individual’s body weight divided by the square of his or her height.

Body Mass Index Bmi

Body Mass Index Bmi

Use the Imperial or Metric formulas below to work out your BMI, then compare it to the charts underneath to see where you sit in terms of your category.

Imperial Formula:

BMI = ( Weight in Pounds
(Height in inches) x (Height in inches)
) x 703

eg. Your height=73 inches, now multiply this by itself. 73×73=5329. Your weight is 176lbs, now divide 176 by 5329. This equals 0.03302. Now lastly multiply this number by 703. 0.03302×703=23.21. So your BMI number is 23.21.

Metric Formula:

BMI = Weight in Kilograms
(Height in Meters) x (Height in Meters)

eg. Your height=1.85 Meters, now multiply this by itself. 1.85×1.85=3.4225. Your weight is 80kg, now divide 80 by 3.4255. This equals 23.23. So your BMI number is 23.23.

The Outcome:

Category BMI range – kg/m2 BMI Prime Mass (weight) of a 1.8 metres (5 ft 11 in) person with this BMI.
Severely underweight less than 16.0 less than 0.66 less than 51.8 kilograms (8.16 st; 114 lb)
Underweight from 16.0 to 18.5 from 0.66 to 0.73 between 51.8 and 59.9 kilograms (8.16 and 9.43 st; 114 and 132 lb)
Normal from 18.5 to 25 from 0.74 to 0.99 between 59.9 and 81.0 kilograms (9.43 and 12.76 st; 132 and 179 lb)
Overweight from 25 to 30 from 1.0 to 1.19 between 81.0 and 97.2 kilograms (12.76 and 15.31 st; 179 and 214 lb)
Obese Class I from 30 to 35 from 1.2 to 1.39 between 97.2 and 113.4 kilograms (15.31 and 17.86 st; 214 and 250 lb)
Obese Class II from 35 to 40 from 1.4 to 1.59 between 113.4 and 129.6 kilograms (17.86 and 20.41 st; 250 and 286 lb)
Obese Class III over 40 over 1.6 from 129.6 kilograms (20.41 st; 286 lb)

Body Mass Index Chart

Body Mass Index Chart

Body Mass Index Chart

Generally speaking a BMI of 25 to 29 is considered overweight whilst a BMI of 30 and over is considered obese.

BMI should be used as a guide in learning your healthly weight range and although it has been used for over 200 years it still give a good estimation of someones healthly weight range. This way of measuring is being superseeded by the more up to date but more complicated system call the Body Volume Index which gives a far more accurate result. Currently the only way the Body Volume Index can be taken is with expensive scanning equipment so is out of the reach for the majority of people.