BMI Calculator

The BMI (body mass index) is a measurement of whether you're a healthy weightfor your height. Use the BMI calculator to check whether your parents are healthy.

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

This calculator should be used for adults (pregnant or lactating mothers should not be relying on the BMI readings) and no decision should be performed based on its numbers aside from consulting a suitably qualified person such as a doctor.

The calculator will give you the information you need to know the way your weight compares with typical values. Body Mass Index (or BMI) is calculated by taking you weight (in kg) 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 the measure of your weight compared to your height. It is crucial to make accurate assessments of obesity. essential as being obese or overweight significantly increases your risk of a variety of medical conditions like type 2 diabetes, heart disease and cancer. With the rate of weight gain or obesity rise the spotlight has been placed onto BMI and its flaws as a measure for ideal weight for an individual instead of whole groups of individuals where "averages" do 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 estimate of your health risks. If your BMI exceeds 35, your weight is definitely putting your health at risk regardless of the other factors below. However, there are some situations where BMI can underestimate or overestimate these risks in the 25-35 BMI range. The most prevalent are:

Children

Your doctor or health visitor can guide you on which side your child is on the 'centile charts' used to calculate healthy weights for children.

Pregnant women

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

If you're very strong

BMI is based on the assumption that you are carrying an adequate amount of fat in your body, including abdominal fat - an abdominal fat that lies deep within your cavity rather than beneath your skin. In fact, abdominal fat is more strongly linked to the risk of type 2 heart disease and diabetes than fat under the skin.

If you're a very strong person your body fat may be less than what is predicted by your BMI. This is only applicable for those who are doing intense exercise higher than average.

If you're of Asian origin, then you should know that.

People of Asian origin are more prone to accumulating intra-abdominal fat (fat in your stomach cavity rather than under your skin) at lower BMI levels than those of Caucasian origin. Individuals who experience this pattern that gain weight are referred to as 'apples' instead of "pears" from their outline. It means that their health risk start to rise at a lower BMI due to the fact that abdominal fat is directly connected to 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 the organisation hasn't changed the cut-off points. However, it has recommended that for public health purposes certain Asian groups should be classified as overweight If their BMI is between 22-25, and obese with an BMI between 26-31.

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

Because muscle mass tends to drop and body fat tends to increase in people who are older However, BMI isn't an accurate measure of body fat levels if you're over 60.

Alternative estimates of weight-related health risk

If you think that your BMI might not accurately tell you if you're overweight or obese by measuring your abdomen circumference, waist, or waist ratio could give you a more realistic estimate.

Waist circumference

Measure your waist circumference approximately halfway between the lower part of your ribcage to the top of your hip bones by putting the tape measure parallel to the floor. You should be breathing out as you measure. Male

• Risk of increased health - >=94cm
• High health risk - >=102cm

Female

• Higher risk of health-related illness - >80cm
• Health risk for high-risk people - > 88cm

Ratio of hip to waist

To check your waist to hip ratio, take a measurement of how wide your waist is (as above) and then your hips' size at the broadest point the hips. Divide your abdominal circumference in relation to your measurements of your hips to determine the ratio.

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

The ratio of height to waist

A recent study on the relationship between BMI the waist circumference, hip-to-waist ratio, and the ratio of waist to height discovered that the most accurate way of determining your overall body weight loss was the waist-height-ratio.

Take your waist circumference measurements as above, and then divide it by the height of your body - clearly both measurements must have either been in imperial (inches) or metric (cm).

The definition of obesity for the whole body is by a waist-height-to-width ratio of:

• 0.53 plus for men
• 0.54 or greater for women

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

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