Body Mass Index (BMI) is commonly used as a preliminary diagnoses in identifying health risks associated with excessive or insufficient weight. It is a simple but useful numeric measurement of fatness or thinness that applies to the average population of average body composition.
The index is based on a person's height and weight using the following formula:
BMI = kg / m2
where kg is a person's weight in kilograms and m2 is their height in metres squared.
BMI is a good general purpose formula for the populace but it does not take body composition into consideration. It does not distinguish between weight due to muscle mass and that of fat mass. Since muscle tissue is denser than fat, it weighs more than fat on a comparative volume basis. Consequently, muscle builders and athletes may show a higher BMI than normal but may not be at all at a greater health risk. In contrast, children, while still growing and developing muscles and the elderly who may be losing muscle may show a lower BMI. Additionally, the body composition of pregnant or lactating women changes dramatically during these periods and so BMI cannot be considered applicable for them.
BMI also does not take body fat distribution into consideration. Studies have shown that excess abdominal fat can also contribute to higher health risks. Use the BMI calculator in conjunction with the other online calculators found on this site such as the Body Shape Index and Waist-to-Hip Ratio calculators for further assessment of your health risk status.
The standard weight categories for BMI is shown in the table below and applies to the average population of adults 20 years or older having average body composition.
|18.5 - 24.9||Normal Weight|
|25 - 29.9||Overweight|
|30 or greater||Obese|
This calculator will calculate your BMI based on your height and weight using the standard BMI formula. It will also calculate the weight for your height at each of the BMI category boundaries using an inversion of the BMI formula:
kg = BMI * m2
where kg is weight in kilograms, BMI is the index at a category boundary, and m2 is your height in meters squared. From this calculation, you will be able to see what the BMI normal healthy weight range is for your height.