BMI Calculator

Determines the body mass index and the ideal weight based on 5 different formulas to help you understand your status.

Body mass index is a simple determination, based on weight and height, that offers information about the weight status of the body and classifies subject in underweight, normal and overweight and obese categories.

The BMI formula is weight in kilograms divided by squared height in meters. This is often used in clinical examinations and as variable for different risk scores and diagnosis tools.

There are tables of average BMI values, gender specific and unspecific, for different countries so one person can compare their weight status to that of people with the same origin.

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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


BMI explained

The body mass index establishes the weight status, namely classifies a person’s weight in an underweight, normal, overweight or obese category.

The above calculator requires the weight and height to compute BMI via:

BMI in the metric system = Weight (kg) / Height (m)2

For those preferring to use the English system, the above transforms into:

BMI = weight (lbs)/ height (in)2 x 703

The country of origin, age and gender are used to provide more insight into the statistics of the BMI in the specified country and to provide a recommended healthy weight.

The body mass index can be used as a way to find out how appropriate the weight of a person is, compared to their height.

BMI can sometimes be found under the name of Quetelet index, from the name of the inventor of the equation: Adolphe Quetelet.

There is also criticism of the formula, as it cannot account for the body composition, meaning that two people with different muscular mass and fat percentage but the same weight and height, would have the same BMI, although their weight status could potentially be different.

For example, an athlete with more muscular mass would potentially be wrongly classified in the overweight range.


Body mass index interpretation

The healthy BMI range is between 18.5 and 25. Values below are identified within gradual underweight categories whilst values above this range, are identified as overweight or obese in different degrees of severity.

The following table introduces the weight categories and their associated BMI values, based on the International Classification of WHO 2004.

Classification BMI (kg/m2)
Severe Underweight <16.00
Moderate Underweight 16.00 - 16.99
Mild Underweight 17.00 - 18.49
Underweight <18.50
Normal range 18.50 - 24.99
Overweight 25.00 - 29.99
Obese I 30.00 - 34.99
Obese II 35.00 - 39.99
Obese III >40.00

Other BMI guidelines

This weight index is most often used to assess the weight status of subjects at risk of being overweight or obese. For example, the following conditions are associated with obesity:

■ Cardiovascular disease;

■ Respiratory diseases;

■ Type 2 diabetes;

■ Metabolic syndrome;

■ Malignancy.

On the other hand, there are also conditions associated with underweight status (BMI lower than 18), such as osteoporosis.

However, people with higher BMI values tend to generally be at a greater illness risk.


IBW formulas

Author Year IBW women IBW men
J.D. Robinson 1983 49 kg + 1.7 kg per inch over 5 feet 52 kg + 1.9 kg per inch over 5 feet
D. R. Miller 1983 53.1 kg + 1.36 kg per inch over 5 feet 56.2 kg + 1.41 kg per inch over 5 feet
B. J. Devine 1974 45.5 kg + 2.3 kg per inch over 5 feet 50.0 kg + 2.3 kg per inch over 5 feet
G. J. Hamwi 1964 45.5 kg + 2.2 kg per inch over 5 feet 48.0 kg + 2.7 kg per inch over 5 feet


1. BMI Classification. (2006) Global Database on Body Mass Index. World Health Organization.

2. Keys A, Fidanza F, Karvonen MJ, Kimura N, Taylor HL. Indices of relative weight and obesity. Journal of Chronic Diseases. 1972; 25 (6–7): 329–43.

Specialty: Fitness

Objective: Determination

Type: Calculator

No. Of Variables: 5

Abbreviation: BMI

Article By: Denise Nedea

Published On: September 7, 2017 · 03:04 AM

Last Checked: September 7, 2017

Next Review: September 7, 2023