BMI Calculator | Body Mass Index Calculator

Body mass index (BMI) is the measure of body fat based on height and weight specific to adult men and women.

BMI is a useful measure that helps to understand if you are overweight and obese. Keep in mind that BMI is an indicative scale only and works on the average of averages, if you are a large frame your BMI may be higher but still within healthy limits (so an athlete will likely have a high BMI score but still have relatively low body fat). Always consult your Doctor if you have concerns about your weight.

BMI is also used to assess the risk of certain diseases. The higher your BMI, the higher your risk for certain diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers. If you have a high BMI and concerns about your health you should consult your Doctor.

Enter your weight and height to view your Body Mass index (BMI)

BMI Calculator
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BMI Calculator. This image shows the BMI formula for the BMI Calculator

How to Calculate your BMI

  1. Enter your height into the BMI Calculator
  2. Enter your weight into the BMI Calculator
  3. The BMI Calculator will calculate your Body Mass Index

What is BMI?

BMI is an acronym for Body Mass Index. BMI is a number that is calculated based on an individuals height and weight. BMI is not, as many believe, a measurement of the amount of body fat, BMI is an indicative number that provides a gauge of an individuals weight based on the BMI index. So, BMI helps you understand if you are overweight (in terms of the BMI Index), it does not help you calculate the amount of body fat you have as the BMI calculation does not factor in specific fat weight, bone weight or muscle weight.

What are the Limitations of the BMI Calculation?

As we discussed above, the BMI math formula does not factor in or calculate specific body fat weight, muscle weight or bone weight. As such, a person who does regular muscle building exercise, athletics, swimming, weight lifting etc. may well go into the obese level on the BMI Index even though they have relatively low levels of body fat (as a ratio of overall body weight).

In addition, the BMI calculation does not allow for an individuals age (other than the separation BMI formula for Adults and children). This means that the adult BMI index encompasses both young and older adults. A senior citizen therefore may well be carrying excess body fat but, because of natural muscle wastage associated with the aging body, appear to be in the normal bracket of the BMI Index.

These two examples underpin why BMI is used as an indicative tool to help avoid certain health issues, it is not as such an exact indicator of specific health.

Does my Ethnicity affect my BMI Calculation?

No, your ethnicity does not affect your BMI calculation but it does allow specific ethnicities to control their BMI to remain within levels which help avoid certain conditions which are more prevalent, for example Black, Asian and other minority ethnic groups have a higher risk of developing type 2 diabetes if their BMI exceeds certain BMI thresholds:

Adults with a BMI of 23 or more are at increased risk of developing some long-term (chronic) conditions, such as type 2 diabetes.

Adults with a BMI of 27.5 or more are at high risk of developing some long-term (chronic) conditions, such as type 2 diabetes.

What is BMI used for?

BMI is used to help identify health problems associated with an individuals weight, whether overweight or underweight. It is important to remember that the BMI calculated number is INDICATIVE, different levels of fitness and activity will cause variation in the BMI indicated bracket on the BMI Index. It is useful therefore to know your BMI score as part of a holistic healthy living plan (including regular exercise and healthy eating regimes). BMI is rarely used on its own to provide an assessment, other measurements of disease risk are also used waist size, chest size etc. to provide a more holistic overview of the individuals health and potential health risks they may be more/less exposed to.

What is the BMI Index?

The BMI Index is a table which defines BMI numeric ranges that, when a calculated BMI figure is computed for an individual, helps identify a defined weight status.

BMI Table
BMIWeight Status
less than 18.5Underweight
18.5 to 24.9Healthy range
25 to 29.9Overweight
40+Morbidly Obese

How is BMI Calculated?

BMI is calculated differently for Children and Adults.

How is BMI Calculated for Adults?

BMI is calculated for Adults using the individuals height and weight. The BMI math formula is:

For Metric BMI Calculations, the BMI math formula is:

BMI = Weight / height2

Where weight is measured in kilograms and height is measured in meters

For Imperial BMI Calculations, the BMI math formula is:

BMI = ( Weight / height2 ) x 703

Where weight is measured in pounds and height is measured in inches

You can of course calculate your BMI using one of the above BMI math formulas or you can use our BMI Calculator by entering your height and weight and choosing your measurement units.

How is BMI Calculated for Children?

BMI for Children and Teens differs based on thier age and sex (boy or girl) so BMI is calculated for children age 2 - 12 and teenagers aged 13 to 19 slightly differently than how BMI is calculated for adults. The same weight and height measurements are used and the figure then applied against the BMI-for-age percentile chart (gender specific) to allow a comparison of the childs weight against a cross section of children in the same age, height and weight group.

BMI-for-age weight status categories and the corresponding percentiles
Percentile RangeWeight Status Category
Less than the 5th percentileUnderweight
5th percentile to less than the 85th percentileNormal or Healthy Weight
85th to less than the 95th percentileOverweight
Equal to or greater than the 95th percentileObese

Health Calculators

You may also find the following Health Calculators useful.

Use of the Health and Medical Calculators

Please note that the Body Mass Index Calculator is provided for your personal use and designed to provide information and information relating to the calculations only. The Body Mass Index Calculator should not be used for you to self-diagnose conditions, self-medicate or alter any existing medication that you are currently prescribed by your Doctor. If the Body Mass Index Calculator produces a calculation which causes you concern, please consult your Doctor for support, advice and further information.