BMI Calculator

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

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

This calculator is only to be used only by adult users (pregnant or lactating women should not rely on the BMI readings) And no action should be made based on its results aside from consulting an appropriately qualified individual like a doctor.

The calculator will give you the information you need to know the way your weight compares with standard values. Body Mass Index (or BMI) is calculated by taking you weight (in kilograms) per square of height (in metres) or BMI = Kg/M2.

Is Body Mass Index reliable?

Your BMI is also known as Body Mass Index, is an indicator of your weight compared to your height. The accuracy of your assessment of obesity is essential as being obese or overweight increases your risk of developing a variety of medical conditions like type 2 heart disease, diabetes and cancer. With the rate of weight gain or obesity rise The spotlight has fallen the spotlight on BMI and its weaknesses as a measure of ideal weight for individual people, 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 most adults, BMI provides a reliable estimate of your health risk. If your BMI is over 35, your weight is most likely to put your health at risk regardless of the variables below. However, there are certain circumstances where BMI might underestimate or exaggerate the risk in the 25-35 BMI range. The most prevalent are:

Children

Your GP or health visitor can guide you on what your child's position is on the 'centile charts' which are used to calculate 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 assumes that you have some body fat, such as 'intra-abdominal' fat - belly fat that's located deep in your cavity, rather than underneath your skin. Intra-abdominal fat is much more strongly linked to the risk of type 2 heart disease and diabetes than fat that is under the skin.

If you're exceptionally muscular the amount of body fat may be lower than expected by your BMI. However, this only applies to those who engage in exercises that are intense - far more than average.

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

People who are of Asian origin are more likely to accumulating intra-abdominal fat (fat deep within your stomach cavity rather than under your skin) with lower BMI levels than those who are of Caucasian origin. People who suffer from this pattern for weight increase are described as 'apples' instead of "pears" in their body outline. This implies that their health risks increase with a lower BMI as the intra-abdominal fat is directly associated with the development of heart diseases and the type 2 form of diabetes.

The World Health Organisation has looked at the evidence and because of the variability between different Asian populations and the different ethnic groups, it hasn't made any changes to the cut-off points. However, it has recommended that for health reasons there are certain Asian groups should be classified as overweight when their BMI is between 22 and 25 and obese if they have BMIs of 26-31.

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

Because muscle mass is known to drop and body fat tends to increase with age however, BMI may not be an accurate gauge of body fat, especially if you're older than 60.

Alternative estimates of health-related weight risk

If you suspect that your BMI does not accurately determine if you're overweight or obese by measuring your abdomen circumference, waisthip or waist ratio may give you an more accurate estimation.

Waist circumference

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

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

Female

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

The ratio of waist to hip

To check your waist to hip ratio, take a measurement of your waist circumference (as above) and your hip size in the broadest point on your hips. Divide your abdominal circumference by your hip measurement to get an approximate ratio.

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

The ratio of height to waist

A recent study on the relationship between BMI along with waist circumference, hip-to-waist ratio, and the waist to height ratio revealed that the most accurate method of predicting your total body fat mass was the waist-height relationship.

You can measure your waist circumference in the same way as above, and then divide the measurement by your height. quite obviously, both measurements should either be in imperial (inches) or the metric (cm).

Body fat is defined by a waist-height ratio of:

• 0.53 or greater for males
• 0.54 plus for females

Abdominal obesity is defined as a waist-to-height proportion of 0.59 or greater.

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