BMI Calculator

The BMI (body mass index) is a measure of whether you're a healthy weightfor your height. Utilize this BMI calculator to find out the adults in your family.

For children, go to Weight Concern's Child and Young people's Body Mass Index (BMI) Calculator. Imperial

The calculator should only be only used to measure the weight of adults (pregnant or lactating women should not rely on these BMI readings) It is not recommended that any action should be determined based on the results beyond consulting an appropriately qualified individual such as a physician.

The calculator can give you an an idea of how your weight is compared to typical values. Body Mass Index (or BMI) is calculated as you weight (in kilograms) times the height of your square (in meters) or BMI = Kg/M2.

Is Body Mass Index reliable?

Your BMI is also known as Body Mass Index, is an indicator of your weight in relation to your height. Accurate assessments of obesity are crucial, since being obese or overweight significantly increases your risk for a variety of medical conditions including type 2 diabetes, heart disease and cancer. As levels of overweight or obesity rise and the focus has been upon BMI and its shortcomings as a measure of ideal weight for an individual instead of whole groups of people for whom 'averages' apply.

"Some people naturally have a larger frame than others. But this causes quite a small variation in weight and is accounted for in the range of healthy BMI. There is really no such thing as someone who is big-boned. " Dr Jan Sambrook, How to lose weight in a healthy way

For the majority of individuals, BMI offers a useful assessment of your weight-related health risk. If your BMI is greater than 35, your weight is certainly putting your health at risk regardless of the variables below. However, there are certain situations where BMI can underestimate or overestimate this risk within the 25 to 35 BMI range. These include:

Children

Your doctor or health visitor can help you determine what your child's position is on the 'centile charts' which are used to calculate the weights that are healthy for children.

Women who are pregnant

Usual BMI estimates do not apply if you're pregnant.

If you're extremely muscular

BMI presumes you've got an acceptable amount of body fat such as 'intra-abdominal' fat - it is the stomach's fat cavity rather than beneath your skin. Fat in the abdominal area is more closely associated with the risk of type 2 heart disease and diabetes than skin fat.

If you're a very strong person then your body fat may be less than expected by your BMI. However, this is only applicable to those who perform high levels of exercise - significantly more than the average.

If you're of Asian origin

People who are of Asian origin are prone to develop intra-abdominal fat (fat deep within your stomach cavity and not beneath your skin) with lower BMIs than those of Caucasian origin. Individuals who experience this pattern with weight gains are referred to as 'apples' and not "pears" as per their body outline. This means their health risks increase when they have a lower BMI due to the fact that abdominal fat is directly related to the development of heart disease and type 2 diabetes.

The World Health Organisation has looked at the evidence and , because of the variability between different Asian populations the organisation hasn't changed the cut-offs. However, it does recommend that for purposes of public health certain Asian groups should be classified as overweight with a BMI of 22-25 and obese if they have an BMI between 26-31.

Older people (over 65, possibly 60)

As muscle mass tends decline and body fat tends to increase in people who are older It is possible that BMI is not an accurate gauge of body fat, especially if you're over 60.

Alternative estimates of health-related weight dangers

If you suspect that your BMI does not accurately determine if you are overweight or obese The measurement of your abdominal circumference, waisthip or waist ratio can provide an more accurate estimation.

Waist circumference

Measure your waist circumference approximately halfway between the lower part of your ribcage to those on the hips' top, using a tape measure that is in line with the floor. The person breathing out must be present when you measure. Male

• Higher risk of developing health issues - >=94cm
• Health risk for high-risk patients - > 102cm

Female

• Increased health risk - >=80cm
• High risk of health-related illness - >=88cm

Ratio hip-to-waist

To determine your waist to hip ratio, measure your waist circumference (as above) as well as your hip size at the widest part on your hips. Divide the circumference of your abdomen by your measurements of your hips to determine the ratio.

• For women, a waist to hip ratio that is greater by 0.85 is associated with higher than average risk.
• For men with a waist to hip ratio greater in excess of 1.00 is associated to a higher than average risk.

Waist to height ratio

A recent study looking at BMI as well as waist circumference, waist-to-hip ratio and the ratio of waist to height found that the most accurate method of determining your fat mass was the waist-height relationship.

Find your waist circumference using the method above, and then divide it by your height - evidently both measurements should soit be measured in imperial (inches) or the metric (cm).

The definition of obesity for the whole body is by a waist-height proportion of:

• 0.53 plus for men
• 0.54 and more in women

Abdominal obesity is defined by a waist-to-height proportion of 0.59 or more.

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