This BMI calculator estimates your body mass index value within BMI range and status coupled with your recommended ideal weight according to 5 different formulas. Below the calculation you can discover the BMI formulas explained and some of their uses.

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How does the BMI calculator work?

This weight tool helps you determine which the body mass index value is and whether this is placed in a healthy range but also other examples of recommended healthy weight according to certain established formulas that are listed below.

In order to complete the task you are required to input your age, gender, height and weight. For the last two you can use either metric or English measurements but please remember that you will receive the results in the same measurement unit in which you input the data. As an extra for this type of calculators you are also asked to choose your country. You might be wonder why is there of reference the country you come from. Well, the BMI calculator will also provide you with the average values of BMI (gender unspecific and gender specific) for your country so you know where you stand between your peers.

The calculation you are to receive are based on the standard BMI formula and some of the most popular ideal weight formulas which were released years ago by scientists such as J.D. Robinson and D.R. Miller in 1983, B.J. Devine in 1974, G.J. Hamwi in 1964 and by the Healthy BMI range recommendation made by the World Health Organization (WHO).

Body Mass Index

The body mass index represents a way of determining how appropriate the weight of a person compared to their height is. It briefly shows whether one has a normal weight, is underweight or maybe overweight. It is also known as the Quetelet index, by the discoverer’s name and is basically an equation that takes into account the weight and height.

This is a very useful but also a full of controversy assessment as it determines the thinness or the thickness of the body in relation to the mass, not having a way to take into consideration what type of weight that is, whether is fat or muscle. This is why this index can’t be used properly in the case of athletes or pregnant women.

How to calculate BMI?

The first formula for BMI in the metric system is: mass (kg)/height (m)^2

The formula in the English system is: mass(lb)/ height (in)^2 * 703

You can find the most known body mass index formulas beside the basic BMI discussed above. These are also formulas used to determine the ideal body weight, another value that points one’s weight to one of the four main categories: underweight, normal, overweight and obese.

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

Example of BMI calculation

For a 28 year old female from the US, weighing 136 lbs at a height of 5 feet and 4 inches, the results from the BMI calculator are as follows:

■ Your BMI is 23.3;

■ Your BMI category is: Healthy weight - Middle Normal;

■ In United States the average BMI (no gender specific) is: 27.82;

■ In United States the average BMI for female is: 27;

■ Your BMI is below the average BMI for female in your country;

■ By using Miller’s formula (1983), your ideal weight is 129.1 lbs;

■ By using Robinson’s formula (1983), your ideal weight is 123 lbs;

■ By using Devine’s formula (1974), your ideal weight is 120.6 lbs;

■ By using Hamwi’s formula (1964), your ideal weight is 119.7 lbs;

■ Your recommended weight, based on the healthy BMI recommendation is between 107.8 lbs and 145.6 lbs.

Body mass index interpretation

There are four main categories in which you can place a BMI value and some of them are further on described. What should be remembered is that the normal healthy range is considered to be between 18.5 and 25.

What it is below means underweight and poses nutritional problems or maybe the existence of an eating disorder while all there is above is overweight and in some cases, obese.

BMI Chart

The values obtained through the formula itself or the above weight tool can be found in the ranges of the BMI table based on the International Classification of WHO 2004.

Classification    BMI (kg/m^2)
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

Why is BMI useful?

The body mass index is a great tool to use as a guideline in order to assess where you stand in terms of your weight and height. Of course we cannot really change our height from the point growth has stopped in young age but we can make fine adjustments to our weight.

For some is an important matter of image while others completely ignore this topic. However, we should all be concerned of the medical implications of our weight. And what a better way to determine if this is a healthy one, but to measure this weight index.

BMI can address many concerns related to weight, obesity level and even up to weight loss and changes in your diet or exercise regime.

BMI implications

As discussed above, the value of this index has a great importance, especially when it doesn’t place one’s weight in the healthy range. What people usually go easy over is that even a small number can imply some health risks. For instance, a BMI lower than 18 predisposes to developing nutritional deficiencies and osteoporosis as some point in life.

It is indeed more to say on higher BMI values as these pose even greater risks so it is important to assess the degree of overweight or obesity.

Continuous clinical research shows some concerning figures and connects obesity to a lot of health impairing conditions such as:

- Cardiovascular diseases (stroke, high blood pressure, coronary disease);

- Respiratory problems (sleep apnea);

- Type 2 Diabetes;

- Metabolic diseases;

- Dyslipidemies (high LDL cholesterol, high triglycerides);

- Gallbladder disease;

- Cancer (i.e colon).


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

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

05 Dec, 2014