Body Mass Index

The BMI Calculator is a useful tool that allows users to calculate their body mass index by entering their height and weight.

The index measures body fat and can be used for adult men and women. It includes several categories - obese, overweight, normal weight, and underweight. Obese individuals fall in one of three categories: very severely, severely, and moderately obese. Individuals with a body mass index of less than 18.5 are considered underweight. Their weight is lower than the normal weight for their height and age group. Factors such as poor nutrition, metabolism, and genes are associated with underweight. Persons with a BMI of 18.5 - 24.9 have normal weight. Basically, it is based on waist circumference, BMI, height, and body type. Even persons with normal weight are at risk if they have a sedentary lifestyle and do not get regular exercise. Overweight persons have an index of 25 - 29.9. For obese persons, this figure is 30 or higher while those who are very severely obese have an index of 40 and higher. As a rule, persons who are underweight have a body fat percentage of under 21 - 24, depending on their age. The healthy range for persons aged 20 to 40 is 21 - 33 percent while obese individuals have a fat percentage of over 39 percent.


The body mass index is a measure that indicates whether a person is at risk for health problems such as stroke, diabetes, high cholesterol, hypertension, gallstones, and coronary artery disease. Obese children, for example, are at risk for many long-term health problems such as liver disease and asthma. The function of the BMI is to measure and assess obesity and weight. It is not a diagnostic tool but a way to check whether you are at risk for health problems associated with being overweight or obese. Thus, it is considered a screening tool while healthcare professionals perform additional assessments. These include family history, level and intensity of physical activity, diet and nutrition, skin thickness measurements, and others.

The BMI value is different for children, depending on their age. It is calculated in percentiles. A value that is in the 1st to 4th percentile indicates that a child is underweight while children who are in the 5th to 84th percentile have a healthy weight. Those in the 85th to 94th percentile are overweight while kids who are in the 96th to 100th percentile are obese. This figure is important because 6 out of 10 teenagers and children with a BMI in the 94th to 100th percentile are at risk for heart problems.

Benefits of Using the Calculator

The good thing about BMI calculators is that they are easy to use. You don't need to be a physician to check your weight status. You just enter your weight and height. Moreover, calculators are free or inexpensive. The index is an indicator of health status that helps people to calculate their desired or ideal weight and corresponding BMI. It is also used to diagnose underweight and malnutrition.


While the calculator is a tool to diagnose overweight and obesity, it doesn't take into account factors such as ethnicity, fitness, physical activity, gender, and age. Muscle mass is not accounted for. For example, athletes may have a high BMI, but this doesn't make them obese. They have large and well developed skeletal muscles. The body mass index of shorter people is also higher. In the view of healthcare professionals, the index is beneficial when used together with other diagnostic tools and tests.

Calculating Your BMI

You can use the following formula: mass (kg)/height (m)2 or mass (lb)/height (in)2 x 703. It is easier to use a calculator, however. For example, a person who weighs 110 pounds and is 5'6" tall has an index of 17.75. This person is underweight. A man who weighs 350 pounds and is 5'10" tall has a BMI of 50.21 which makes him very severely obese. If you are 5'7" and weigh 130 pounds, your index will be 20.36, and you have a healthy weight.