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BMI Calculator

What is BMI?

BMI or Body Mass Index is a calculation to see if your bodyweight is healthy. It uses you weight and height.


Use our simple BMI calculator below:

Your BMI is

BMI ranges

  • below 18.5 – you’re in the underweight range
  • between 18.5 and 24.9 – you’re in the healthy weight range
  • between 25 and 29.9 – you’re in the overweight range
  • between 30 and 39.9 – you’re in the obese range

According to the NHS.

Be aware, although your BMI  is a good indication as to if you’re carrying too much weight. It cannot tell you if you are carrying too much fat.

This means:

  • If you are a muscular adult you may be classed “overweight” or “obese” even though your body fat is low.
  • As you get older and lose muscle, you may fall into the “healthy weight” range even though you may be carrying excess fat.

whats my bmi

How to calculate BMI

BMI is calculated by dividing your weight in kilograms by your height in metres squared.

Situations where BMI is less reliable?

In general, BMI is a useful measure for most adults. However, BMI results may be a less reliable indicator for some groups of people, including:

Athletes, and those with a lot of muscle

some ethnic groups

older people

pregnant women

those less than 1.5m/5ft tall

children and teenagers

if your BMI is below 18.5, this puts you in the underweight range. Being underweight isn’t good for your health. Please speak to your GP as they can offer help and advice

If you, or the individual you are measuring, belongs to one of these categories you should speak to a doctor or other health professional to get a more accurate measurement.

What to do if I’m worried about my BMI results?

If our BMI calculator finds that your BMI is outside of the healthy range, we recommend you talk to your doctor before making any really big changes to your diet or the amount of physical activity you do.

However, don’t let that stop you making small changes today. If the BMI calculator finds you are more than the ideal weight, losing just a few pounds is a great start, and can improve your health and help to lower your risk of cancer and other diseases. If your BMI indicates you are less than the ideal weight, gaining some weight could benefit your health.