BMI Calculator

BMI (body mass index) is a measure of whether you're a healthy weightfor your height. Make use of this BMI calculator to determine those in the family who are adults.

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

This calculator is only to be used to measure the weight of adults (pregnant or lactating women shouldn't rely on these BMI readings) however, no action should be decided based upon its findings apart from consulting an appropriately qualified professional like a doctor.

The calculator will give you an an idea of how your weight compares to standard values. Body Mass Index (or BMI) is calculated by taking your mass (in kilograms) subtracted by the size of the square (in metres) or BMI = Kg/M2.

Is Body Mass Index reliable?

Your BMI, or Body Mass Index, is an index of your weight in comparison to your height. It is crucial to make accurate assessments of obesity. crucial, since being obese or overweight significantly increases your risk of a variety of medical conditions including type 2 heart disease, diabetes, and cancer. When the prevalence of overweight or obesity increase, the spotlight has fallen on BMI and its shortcomings as a measure of ideal weight for individuals, rather than whole populations of people for whom '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 adult people, BMI can provide a solid assessment of your weight-related health risk. If your BMI is higher than 35, you're most likely to put your health at risk regardless of the variables below. However, there are some circumstances where BMI could be over or underestimating the risk in the 25-35 BMI range. The most common are:

Children

Your doctor or health visitor can help you determine where your child sits on the 'centile charts' that are used to determine healthy weights for children.

Pregnant women

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

If you're extremely strong

BMI assumes you have an average amount of body fat, which includes 'intra-abdominal fat', fat deep inside your stomach cavity, not under your skin. The abdominal fat is more closely associated with the risk of type 2 heart disease and diabetes than skin fat.

If you are very muscular the amount of body fat might be lower than expected by your BMI. However, this only applies to those who perform rigorous exercise much more than average.

If you are of Asian origin

People of Asian origin are more likely to develop abdominal fat (fat in your stomach cavity and not under your skin) with lower BMI levels than those who are of Caucasian origin. People with this pattern with weight gains are described as 'apples' , rather than "pears" as per their body outline. It means that their health risk start to rise at a lower BMI as the intra-abdominal fat is directly connected to the development of heart disease as well as kind 2 diabetes.

The World Health Organisation has looked at the evidence and , because of the wide range of Asian populations, it hasn't officially changed the cut-offs. However, it does recommend that for health reasons there are certain Asian groups should be considered overweight if their BMI is 22-25, and obese with a BMI of 26-31.

People who are older (over 65, possibly 60)

As muscle mass tends fall and body fat is likely to rise in people over 60 The BMI might not be an accurate gauge of body fat when you're over 60.

Alternative estimates of health-related weight risk

If you feel BMI may not accurately indicate whether you are overweight or obese by measuring your abdomen circumference, waist-hip or waist ratio may give you an estimate that is more accurate.

Waist circumference

You measure your waist circumference about halfway between the bottom of your ribcage to above your hip bones, by putting the tape measure in line with the floor. You should be breathing out while you take measurements. Male

• Health risk increased - > 94cm
• High health risk - >=102cm

Female

• Health risk increased - >80cm
• Health risk for high-risk people - > 88cm

Ratio hip-to-waist

To measure your waist-to- hip ratio, take a measurement of how wide your waist is (as above) and your hip size in the widest area the hips. Divide the circumference of your abdomen by your hip measurement for the ratio.

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

Ratio of waist to height

A recent study comparing BMI and waist circumference with hip to waist ratio and the ratio of waist to height found the most reliable method of determining your 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).

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

• 0.53 plus for men
• 0.54 or more for women

Abdominal obesity was defined by an waist-to-height ratio of 0.59 or more.

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