BMI Calculator

BMI (body mass index) is a measure of your healthy weightfor your height. Use this BMI calculator to check for the parents in your home.

For children, go to Weight Concern's Child page and the young adult's weight index (BMI) calculater. Imperial

This calculator is only to be used to measure the weight of adults (pregnant or lactating mothers should not be relying in these BMI readings) And no action should be taken based on its values other than consulting a suitably qualified person like a doctor.

The calculator will give you an an idea of how your weight stands up to typical values. Body Mass Index (or BMI) is calculated by taking how much weight (in kg) 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 a measure of your weight relative to your height. Accurate assessments of obesity are crucial, since being obese or overweight significantly increases the risk of contracting a variety of medical conditions like type 2 heart disease, diabetes, and cancer. With the rate of weight gain or obesity increase, the spotlight has fallen on BMI and its shortcomings as a measure of optimal weight for individuals, rather than whole populations of people where "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 adults, BMI gives a good idea of your health risks. If your BMI is over 35, your weight is sure to put your health in risk regardless of the risk factors below. However, there are some circumstances where BMI could be over or underestimating those risks for the 25-35 BMI range. The most common are:

Children

Your doctor or health visitor can guide you on the place your child should be on the "centile charts," which are used to calculate healthy weights for children.

Pregnant women

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

If you're very muscular

BMI assumes that you have an average amount of body fat including abdominal fat - the fat that is located in your stomach cavity, rather than underneath your skin. In fact, abdominal fat is more closely linked to risks of type 2 diabetes and heart disease than fat under the skin.

If you're extremely muscular the amount of body fat may be lower than expected by your BMI. However, this is only applicable to those who perform exercises that are intense - much more than average.

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

People who are of Asian origin are more prone to accumulate abdominal fat (fat that is located deep in your stomach cavity rather than under your skin) with lower levels of BMI than those of Caucasian origin. People with this pattern with weight gains are described as 'apples' , rather than 'pears' from their body outline. The health risks increase when they have a lower BMI, because intra-abdominal fat is directly associated with the development of heart disease, and the type 2 form of diabetes.

The World Health Organisation has looked at the evidence, and because of the varying characteristics between Asian populations, it hasn't officially changed the cut-offs. However, it recommends that for purposes of public health certain Asian populations should be classified as overweight with a BMI of 22-25 or obese with BMIs between 26 and 31.

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

Since muscle mass tends to fall and body fat is likely to increase in older individuals The BMI might not be an accurate measure of body fat levels if you're older than 60.

Alternative estimates of health-related weight dangers

If you are concerned that BMI may not accurately tell you if you're obese or overweight taking a look at your abdominal circumference, waisthip or waist ratio could provide you with a more realistic estimate.

Waist circumference

You can measure your waist circumference halfway between the bottom of your ribcage to high-top of your hip bones with the tape measure parallel to the floor. It is essential to breathe out when you measure. Male

• Health risk increased - > 94cm
• Health risk for high-risk patients - > 102cm

Female

• Health risks increased by >=80cm
• Health risks for the elderly >= 88cm

The ratio of waist to hip

To measure your waist-to- hip ratio, measure your waist circumference (as above) and then your hips' size at the widest portion of your hips. Divide the circumference of your abdomen by your hip measurement to get an approximate ratio.

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

Waist to height ratio

A recent study looking at BMI, waist circumference, waist to hip ratio as well as the waist to height ratio revealed that the most reliable method of determining your overall body fat content was the waist-height ratio.

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

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

• 0.53 or higher for men
• 0.54 or more for women

Abdominal obesity is defined as a waist-height ratio of 0.59 or more.

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