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BMI, or body mass index, is a measurement generally used to gauge the healthiness of a person’s weight. Invented by a physician called Quetelet in the early 1900s, BMI is widely used as a rough indicator of body mass health.

So, how is BMI calculated? You need two measurements to check on your body mass index: your height and your weight. Then, simply follow the formula below to get a reading, and compare your result to the BMI ranges recommended by the NHS.

If you’ve been thinking about weight management and the health of your heart, there’s no harm in finding out how to calculate your BMI. Just remember to always get the opinion of a healthcare professional before making key decisions about weight.

Why should I be calculating BMI?

BMI can indicate whether a person’s weight is healthy, taking into account their height as well. Being overweight can mean that you’re more likely to have elevated cholesterol levels, so keeping an eye on your BMI (and managing it) is one way you can help to maintain heart health.

However, you should be aware that BMI does not factor in physical fitness – your body mass index could be high if you’ve built up a lot of muscle, rather than fat. If you’re looking at your weight with a healthcare professional, they might wish to also do the following:

  • Measure your waist circumference (just above the top of your pelvis), as this measurement alongside a BMI reading can give them a better picture of your health.
  • They’re also likely to have a chat with you about your overall diet and lifestyle.

And, if you wish to make some positive changes on your lifestyle and start eating more healthily, check out these tips that Flora ProActiv has put together.

How to calculate BMI infograph

How to calculate BMI: The formula

When calculating your BMI, you’ll need your weight in kilograms and your height in meters.

If you want to know how to calculate BMI manually, the formula is as follows:

KG/M2 or, weight in kilograms divided by (height in meters multiplied by height in meters)

So, to enter this on a normal calculator, follow these steps:

  1. Height x height = height squared
  2. Kilograms ÷ height squared = BMI

Once you have your BMI, read our guide to healthy BMI readings here to find out if you are in a healthy BMI range.

How can I lower my BMI?

You might like to try the following:

  • Schedule regular exercise, at least three times a week.
  • Balance your diet.
  • Reduce your portion sizes.
  • Cut down your energy intake by eating less high sugar and high saturated fat foods.
  • Choose active options every day – take the stairs instead of the lift, walk instead of getting the bus, and so on.
  • Visit your GP regularly if you have any questions or need information on how to build a healthy lifestyle.

Things to consider when calculating BMI

BMI isn’t strictly accurate, as a range of contributing factors can affect your weight, from muscle, to age, to conditions such as an overactive thyroid.

BMI also rarely has a lower weight bracket, which could lead very underweight and elderly people to believe they are a safe weight.

For these reasons, if you want to know how to calculate your BMI manually, never take your result as fact, and always ask a health professional for their assessment. Remember – BMI is used as an indicator alongside other measurements, not a rule by itself.

This information has been included in good faith, but is for general informational purposes only, and should not be construed as a guarantee. The nutritional facts and statements on this site are designed for educational and resource purpose sonly, not being substitutes for professional advice. If you have any concerns or questions about your health, you should always check with your GP or healthcare professional.