BMI Calculator

The BMI (body mass index) is a measure of your healthy weightfor your height. Make use of this BMI calculator to determine all the adult members of your household.

For children, visit Weight Concern's Child page and the young the body mass index (BMI) calculator. Imperial

This calculator should only be only used only by adult users (pregnant or lactating women should not rely on these BMI readings) It is not recommended that any action should be made based on its results beyond consulting a suitably qualified person such as a doctor.

The calculator will give you an the information you need to know how your weight is compared to the norm for values. Body Mass Index (or BMI) is calculated as your mass (in kilograms) times the height of your square (in metres) 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 important, as being obese or overweight significantly increases the risk of developing a variety of medical conditions like type 2 heart disease, diabetes and cancer. When the prevalence of overweight or obesity rise the spotlight has shifted on BMI and its limitations as a measure of optimal weight for people instead of a whole population 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 most adults, BMI is a great assessment of your weight-related health risk. If your BMI is above 35, you're definitely putting your health at risk, regardless of the factors below. But, there are situations where BMI might underestimate or exaggerate those risks for the 25-35 BMI range. The most prevalent are:

Children

Your GP or health visitor can advise on where your child sits on the "centile charts," used to calculate healthy weights for children.

Women who are pregnant

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

If you're extremely muscular

BMI assumes you have an average amount of body fat, including intra-abdominal fat, it is the stomach's fat cavity rather than under your skin. In fact, abdominal fat is more closely linked with risk of type 2 diabetes and heart disease than fat beneath the skin.

If you're exceptionally muscular then your body fat could be lower than what is predicted by your BMI. But, this is only applicable for those who are doing extreme amounts of exercise - substantially more than the average.

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

People who are of Asian origin are more likely to build up abdominal fat (fat in your stomach cavity , rather than beneath your skin) with lower BMI than those who are of Caucasian origin. People who suffer from this pattern with weight gains are referred to as 'apples' and not "pears" from their outline. The health risks begin to increase at lower BMI due to the fact that abdominal fat is directly connected to the development of heart diseases and types 2 diabetes.

The World Health Organisation has looked at the evidence and because there is a wide variation between Asian populations however, they haven't yet officially altered the cut-offs. However, the WHO recommends that , for the sake of public health some Asian groups are considered overweight If their BMI is between 22-25 and obese if they have BMIs of 26-31.

People who are older (over 65, possibly 60)

As muscle mass tends drop and body fat tends to increase in older individuals The BMI might not be an accurate indicator of body fat if over 60.

Alternative estimates of health-related weight dangers

If you are concerned that BMI may not accurately tell you if you're overweight or obese the measurement of your waist circumference, waist-hip or waist ratio can give you an more accurate estimation.

Waist circumference

Measure your waist circumference halfway between the bottom of your ribcage and above your hip bones, by putting the tape measure parallel to the floor. You must be breathing out as you measure. Male

• Increased risk of health problems - >=94cm
• High risk of health - > 102cm

Female

• Health risk increased - >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) and then your hip size in the widest area of your hips. Divide the circumference of your abdomen by your hip measurement to calculate an amount.

• In women, a waist-to- hip ratio higher over 0.85 is associated to a higher than average risk.
• For men the waist-to-hip ratio of more than 1.00 is associated to a higher than average risk.

Ratio of waist to height

A study conducted recently comparing BMI, waist circumference, hip-to-waist ratio, and waist to height ratio found that the most reliable method of predicting your total body weight loss was the waist-height-ratio.

The waist circumference should be measured as above and simply divide it by height. evidently both measurements should either be in imperial (inches) or metric (cm).

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

• 0.53 plus for men
• 0.54 plus for females

Abdominal weight gain is measured by an waist-to-height ratio of 0.59 or more.

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