BMI Calculator

The BMI (body mass index) is a measure of your healthy weightfor your height. Utilize the BMI calculator to measure those in the family who are adults.

For children, visit Weight Concern's Child and Young individual's body mass index (BMI) Calculator. Imperial

This calculator is only to be only used by adults (pregnant or lactating ladies should not rely on these BMI readings) And no action should be performed based on its numbers aside from consulting an appropriately qualified individual like a doctor.

The calculator can give you an the idea of how your weight compares to the norm for values. Body Mass Index (or BMI) is calculated by taking how much weight (in kg) subtracted by the size of the square (in meters) or BMI = Kg/M2.

Is Body Mass Index reliable?

Your BMI, or Body Mass Index, is the measure of your weight in relation to your height. The accuracy of your assessment of obesity is important, as being overweight or obese increases your risk of a variety of medical conditions like type 2 diabetes, heart disease and cancer. As levels of excess weight or obesity rise and the focus has been upon BMI and its shortcomings as a metric of ideal weight for individuals instead of whole groups of people , where the '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 can provide a solid estimate of your health risks. If your BMI is greater than 35, you're sure to put your health in risk regardless of the other factors below. However, there are certain circumstances where BMI could underestimate or overestimate this risk within the 25 to 35 BMI range. These include:

Children

Your physician or health visitor can guide you on where your child sits on the "centile charts" used to estimate the healthy weights of children.

Pregnant women

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

If you're very muscular

BMI assumes you've equal amounts of body fat, which includes 'intra-abdominal fat', belly fat that's located deep in your cavity instead of under your skin. Intra-abdominal fat is much more closely linked to risks of type 2 diabetes and heart disease than skin fat.

If you're very muscular the amount of body fat may be less than predicted by your BMI. This only applies to people who do exercises that are intense - significantly more than the average.

If you are of Asian origin

People who are of Asian background are more likely to accumulate abdominal fat (fat that is located deep in your stomach cavity rather than beneath your skin) with lower levels of BMI than those of Caucasian origin. The people who have this type with weight gains are described as 'apples' instead of 'pears' from their body outline. This implies that their health risks increase when they have a lower BMI since abdominal fat is directly connected 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-off points. However, it does recommend that , for the sake of public health certain Asian groups should be classified as overweight in the event that their BMI falls between 22-25, and obese with BMIs of 26-31.

People who are older (over 65, possibly over 60)

Because muscle mass is known to decline and body fat tends to increase in people who are older however, BMI may not be an accurate reflector of body fat if over 60.

Alternative estimates of weight-related health dangers

If you are concerned that BMI may not accurately determine if you are overweight or obese, measuring your abdominal circumference, waist-hip or waist-height ratio can give you an accurate figure.

Waist circumference

Measure your waist circumference halfway between the bottom of your ribcage to those on the hips' top, with the tape measure parallel to the floor. You must breathe out when you measure. Male

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

Female

• Higher risk of health-related illness - >80cm
• Risk of high health - >=88cm

Ratio hip-to-waist

To measure your waist-to- hip ratio, take a measurement of your waist's circumference (as above) and your hip measurement at the widest part of your hips. Divide your abdominal circumference by your hip measurement to calculate an approximate ratio.

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

Waist to height ratio

A study conducted recently comparing BMI and waist circumference with waist-to-hip ratio and the waist-to-height ratio discovered that the most accurate method of predicting your whole-body fat level was waist-height ratio.

The waist circumference should be measured as above and simply divide it by the height of your body - fairly obviously both measurements should at least be imperial (inches) or metric (cm).

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

• 0.53 plus for men
• 0.54 or more for women

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

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