BMI Calculator

BMI (body mass index) is a measure of whether you're a healthy weightfor your height. Use the BMI calculator to check all the adult members of your household.

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

This calculator should be employed in the case of adult (pregnant or lactating ladies should not rely in these BMI readings) And no action should be determined based on the results other than to consult an appropriately qualified individual such as a doctor.

The calculator will give you the information you need to know how your weight compares to standard values. Body Mass Index (or BMI) is calculated as your mass (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 an indication of your weight in comparison to your height. The accuracy of your assessment of obesity is crucial, since being obese or overweight significantly increases your risk for a range of medical conditions such as type 2 heart disease, diabetes and cancer. With the rate of weight gain or obesity increase the spotlight has been placed the spotlight on BMI and its shortcomings as a measure for ideal weight for an individual as opposed to a complete population of people for whom "averages" are used.

"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 gives a good idea of your health risk. If your BMI is above 35, you're certain to put your health at risk, regardless of the factors below. But, there are circumstances in which BMI might underestimate or exaggerate this risk within the 25 to 35 BMI range. The main ones are:

Children

Your physician or health visitor can guide you on where your child sits on the 'centile charts' that measure the healthy weights of children.

Women who are pregnant

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 adequate amount of fat in your body, including 'intra-abdominal fat' - fat deep inside your stomach cavity instead of under your skin. In fact, abdominal fat is more closely linked with risk of type 2 diabetes and heart disease than skin fat.

If you are very muscular the amount of body fat could be less than what is predicted by your BMI. However, this is only applicable to those who perform intense exercise significantly more than the average.

If you're of Asian or Asian descent, you're in the right place.

People of Asian origin are prone to develop abdominal fat (fat that is located deep in the stomach cavity, not beneath your skin) with a lower BMI than people of Caucasian origin. Individuals who experience this pattern of weight gain are described as "apples" rather than "pears" from their body outline. This implies that their health risks are increased at lower BMI as the intra-abdominal fat is directly linked with the development of heart disease, and Type 2 Diabetes.

The World Health Organisation has looked at the evidence and because there is a wide variation between Asian populations the organisation hasn't changed the cut-off points. But, it does suggest to use the cut-off points for public health there are certain Asian populations should be classified as overweight if their BMI is 22-25 and obese with a BMI of 26-31.

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

Because muscle mass tends decline and body fat tends to increase with age however, BMI may not be an accurate reflector of body fat when you're over 60.

Alternative estimates of health-related weight risks

If you suspect that your BMI does not accurately tell you if you're overweight or obese the measurement of your waist circumference, waist-hip or waist-height ratio could provide you with a more realistic estimate.

Waist circumference

The waist circumference is measured half way between the bottom of your ribcage to at the highest point of the hip bone, by putting the tape measure parallel to the floor. You should be breathing out as you measure. Male

• Higher risk of developing health issues - >=94cm
• High risk of health - > 102cm

Female

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

Ratio hip-to-waist

To determine your waist to hip ratio, take a measurement of you waist circumference (as above) and then your hip size in the widest point the hips. Divide the circumference of your abdomen by your hip measurement to get an amount.

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

The ratio of height to waist

A recent study looking at BMI along with waist circumference, hip to waist ratio and waist to height ratio found that the best method of predicting your total body fat level was waist-height ratio.

Find your waist circumference using the method above and simply divide it by your height . clearly both measurements must have either been in imperial (inches) or metric (cm).

Obesity in the whole body is defined by a waist-height ratio of:

• 0.53 and more males
• 0.54 or greater for women

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

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