How to Calculate Your BMI
For many people, weight control is all about looking fit and trim. Weight loss, though, isn’t as simple as having an hourglass figure or having no fat at all. Weight loss has as much to do with crunching numbers as it does with calories. To get the right weight for your body type, you have to calculate your body mass index (BMI) before committing yourself to a weight loss or exercise program.
What is the Body Mass Index?
Body mass index (BMI) is the ratio between your height and weight. It is also known as the Quetelet index. It is a useful way to determine ideal body weight depending on a person’s height. BMI is a simple way of knowing whether or not a person is underweight, obese, or falls within the normal and acceptable weight range for a given height. Body mass indexes are useful for:
Diet plans. If you plan to shed pounds through dieting or to build mass through a specialized diet, your ideal BMI can help you choose a diet plan for yourself.
Exercise programs. Exercise can also help you manage your weight. The BMI is useful if you want to design an exercise plan.
Social applications. Weight control is an important social issue. BMI is often used by health agencies to determine the overall weight of a population.
Calculating the BMI
BMI is a ratio expression, which means that it can be derived through a simple process of division. The BMI value can be calculated either through metric units or through English units. To derive your BMI value, prepare the following:
Tape measure or body height scale
Weighing scale
Calculator or scrap paper
BMI chart
Instructions
Get the values of your weight and height. Make sure that you’re using the right unit values. When using pounds for weight, use inches or feet for height. When using meters for height, use kilograms for weight.
Divide the weight by the square of the height.
When using English or US measuring values, multiply the weight by a value before dividing it by the square of the height. For inches, multiply the weight by 703. For feet, multiply the weight by 4.88.
Body Mass Ranges
BMI can be expressed either as BMI range or BMI prime. BMI range is a value of the BMI result noted in kilograms per square meter. BMI prime is a range of values that results from the ratio between the actual BMI value, and the upper limit BMI value. For most BMI charts, the upper limit is set at 25.
Results of the BMI depend on the relationship or ratio of height and weight. Over the years, many categories have been included in the BMI chart to accommodate varying degrees of obesity. There are 10 different categories in a typical BMI chart:
Severely underweight: BMI value of 16.5 kg/m2 or less, BMI prime of less than 0.66
Underweight: BMI value between 16.5 and 18.5, BMI prime between 0.66 and 0.74
Normal: BMI value between 18.5 to 25, BMI prime between 0.74 to 1.00
Overweight: BMI value between 25 to 30, BMI prime between 1.0 to 1.2
Class I obese: BMI value between 30 to 35, BMI prime between 1.2 to 1.4
Class II obese: BMI value between 35 to 40, BMI prime between 1.4 to 1.6
Severely obese: BMI value between 40 to 45, BMI prime between 1.6 to 1.8
Morbidly obese: BMI value between 45 to 50, BMI prime between 1.8 to 2.0
Super obese: BMI value between 50 to 60, BMI prime between 2.0 to 2.4
Hyper obese: BMI value above 60, BMI prime above 2.4
Keep in mind that BMI can only determine the ratio of your height to your weight, and does not count other factors like bone mass and muscle mass. Think of the body mass index as one of the many useful tools that you can use to lose excess weight, and keep a fit, trim, and healthy lifestyle.