BMI Calculator

BMI (body mass index) is a measure of your healthy weightfor your height. Make use of this BMI calculator to check 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

The calculator should only be used by adults (pregnant or lactating women should not base their decisions solely on BMI readings) It is not recommended that any action should be taken based on its values other than to consult an appropriately qualified individual like a doctor.

The calculator will give you an insight into the way your weight compares with common values. Body Mass Index (or BMI) is calculated by taking your mass (in kilograms) 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 a measure of your weight in relation to your height. A precise assessment of obesity is crucial, since being obese or overweight significantly increases your risk of developing a variety of medical conditions including type 2 diabetes, heart disease and cancer. As the levels of obesity or obesity increase The spotlight has fallen to BMI and its flaws as a gauge of the ideal weight for individual people as opposed to a complete population of people where "averages" will 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 individuals, BMI gives a good assessment of your weight-related health risk. If your BMI is greater than 35, you are definitely putting your health at risk, regardless of the factors below. However, there are certain instances where BMI could be over or underestimating the risk in the 25-35 BMI range. These include:

Children

Your doctor or health visitor can provide advice on where your child sits 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 very strong

BMI presumes you've got an adequate amount of fat in your body, including intra-abdominal fat, it is the stomach's fat cavity, not under your skin. Intra-abdominal fat is much more closely associated with the risk of type 2 diabetes and heart disease than fat beneath the skin.

If you're a very strong person the amount of body fat could be lower than that predicted by your BMI. But, this is only applicable to those who perform high levels of exercise - substantially more than the average.

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

People who are of Asian heritage are more susceptible to accumulating intra-abdominal fat (fat deep within your stomach cavity instead of beneath your skin) at a lower BMI than people of Caucasian origin. Individuals who experience this pattern in weight loss are referred to as 'apples' instead of "pears" from their outline. It means that their health risk start to rise at a lower BMI as the intra-abdominal fat is directly linked with development of heart disease and type 2 diabetes.

The World Health Organisation has looked at the evidence and because of the variability between different Asian populations, it hasn't officially changed the cut-off points. However, it has recommended that for purposes of public health that certain Asian populations should be classified as overweight in the event that their BMI falls between 22-25, and obese with an BMI between 26-31.

Older people (over 65, possibly over 60)

Since muscle mass tends to fall and body fat is likely to increase in people who are older, BMI may not be an accurate reflector of body fat if older than 60.

Alternative estimates of health-related weight dangers

If you feel BMI may not accurately tell you if you're overweight or not by measuring your abdomen circumference, waist-hip , or waist-height ratio could give you an more accurate estimation.

Waist circumference

You can measure your waist circumference at a half-way point between the bottom of your ribcage to above your hip bones by putting the tape measure in line with the floor. You must breathe out while you take measurements. Male

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

Female

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

Ratio of hip to waist

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

• For women, a waist-to- hip ratio of more that 0.85 is associated with higher than the average risk.
• In men, a waist to hip ratio greater then 1.00 is associated with higher than the 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 discovered that the most accurate method of determining your overall body fat level was waist-height ratio.

Find your waist circumference using the method above and simply divide the measurement by your height. quite obviously, both measurements should either be in imperial (inches) or metric (cm).

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

• 0.53 and more men
• 0.54 and more in women

Abdominal obesity is defined as the waist-to-height ratio of 0.59 or greater.

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