BMI Calculator

The BMI (body mass index) is a measure of your healthy weightfor your height. Use this BMI calculator to measure the adults in your family.

For children, go to Weight Concern's Child and young person's body mass index (BMI) Calculator. Imperial

The calculator should only be used for adults (pregnant or lactating mothers should not be relying in these BMI readings) It is not recommended that any action should be taken based on its values aside from consulting an appropriately qualified professional such as a doctor.

The calculator can give you an insight into how your weight compares to normal values. Body Mass Index (or BMI) is calculated as your mass (in kilograms) divided by the square of your height (in meters) or BMI = Kg/M2.

Is Body Mass Index reliable?

Your BMI, or Body Mass Index, is an indicator of your weight compared to your height. A precise assessment of obesity is essential, as being obese or overweight increases your risk of a variety of medical conditions like type 2 heart disease, diabetes, and cancer. As levels of excess weight or obesity increase the spotlight has been placed to BMI and its shortcomings as a measure for ideal weight for individuals and not for whole groups of people to 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 adult people, BMI gives a good idea of your health risk. If your BMI exceeds 35, you are certain to put your health at risk regardless of the reasons below. But, there are circumstances in which BMI could be over or underestimating these risks within the 25-35 BMI range. The most prevalent are:

Children

Your physician or health visitor can guide you on what your child's position is on the "centile charts" used to calculate the healthy weights of children.

Pregnant women

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

If you're extremely muscular

BMI is based on the assumption that you are carrying an acceptable amount of body fat, which includes 'intra-abdominal fat', fat deep inside your stomach cavity, not under your skin. The abdominal fat is more closely linked to risks of type 2 heart disease and diabetes than skin fat.

If you're very muscular, your level of body fat might be lower than what is predicted by your BMI. This is only applicable to those who engage in high levels of exercise - substantially more than the average.

If you're of Asian Origin, you will be able to identify yourself.

People who are of Asian origin are prone to develop intra-abdominal fat (fat within your stomach cavity instead of beneath your skin) at a lower BMI than people who are of Caucasian origin. People who exhibit this pattern of weight gain are described as 'apples' and not "pears" from their outline. This means their health risks increase when they have a lower BMI since 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 wide range of Asian populations however, they haven't yet officially altered the cut-offs. However, it recommends that , for the sake of public health some Asian groups should be considered overweight If their BMI is between 22-25, and obese with the BMI range of 26 to 31.

Older people (over 65, perhaps over 60)

Because muscle mass tends to fall and body fat is likely to rise in older people However, BMI isn't an accurate indicator of body fat levels if you're older than 60.

Alternative estimates of weight-related health dangers

If you are concerned that BMI may not accurately determine if you are overweight or obese The measurement of your abdominal circumference, waist-hip , or waist-height ratio could give you an more accurate estimation.

Waist circumference

You can measure your waist circumference halfway between the bottom of your ribcage to those on the hips' top using a tape measure that is in line with the floor. It is essential to breathe out when you measure. Male

• Health risk increased - > 94cm
• High health risk - >=102cm

Female

• Risk of increased health - >80cm
• High health risk - >=88cm

Waist to hip ratio

To determine your waist to hip ratio, take a measurement of you waist circumference (as above) as well as your hip size in the widest point on your hips. Divide your abdominal circumference by your measurements of your hips to determine an amount.

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

Ratio of waist to height

A study conducted recently comparing BMI along with waist circumference, hip to waist ratio and the waist-to-height ratio discovered that the best method to determine your body fat mass was the waist-height relationship.

Take your waist circumference measurements as above and simply divide it by your height . clearly both measurements must or be either in imperial (inches) or metric (cm).

Whole body obesity is determined by a waist-height ratio of:

• 0.53 and more men
• 0.54 plus for females

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

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