BMI calculation

BMI or body mass index is calculated using height and weight measurements to assess your body fat. Also known as the Quetelet index, the BMI index scale was developed by a Belgium statistician called Adolphe Quetelet in the 1800’s. Quetelet established bmi measurement, this simple measurement for classifying peoples' weight relative to an ideal weight for their height know as the BMI scale.

Body mass index can be calculated using metric or imperial figures. It is defined as your body weight divided by the square of your height when using metric figures of kilograms and metres. It produces a unit of measure of kg/m². When using imperial pounds and inches the formula needs altering slightly to adjust it to the same BMI values as those calculated using metric units. This enables the universal use of a BMI score.

You can work out your BMI here.

BMI checker 

Metric BMI formula
BMI Calculator KG = Weight (kg) / Height (m)²
The metric formula for BMI is weight in kilograms divided by height in meters squared. Often height is measured in centimetres. To convert your height to meters simply divide your height in centimetres by 100.

For example
If you’re height is 175cm and your weight is 75kg your BMI is calculated as follows:
75kg / (1.75m²) = 24.49kg/m²

Imperial BMI formula
BMI = [Weight (lbs) / Height (inches)²] x 703
The imperial formula requires you to divide your weight in pounds by your height in inches, squared. This figure is then multiplied by a conversion factor of 703.

For example
If you’re 5’5” (65 inches) in height and your weight is 150 pounds you BMI is calculated as follows:
[150lbs / (65 inches²)] x 703 = 24.96

BMI calculator

To calculate your BMI you can visit here to get your BMI test. This body mass calculator allows you to simply enter your height and weight figures in either metric or imperial values and your BMI is computed for you.

You can bookmark this page if you’re monitoring your BMI maybe as part of a weight loss programme or just to keep abreast of your BMI and maintain a healthy BMI status.

What does your BMI value mean?

BMI is interpreted using standard weight status categories. These categories are the same for all adults, for both men and women, for all body types and they are age independent.

What is a healthy bmi?

Below 18.5 - Underweight
18.5 to 24.9  - Normal or Healthy Weight
25.0 to 29.9 - Overweight
30.0 and Above - Obese

BMI of less than 18.5

If you’ve a BMI of less than 18.5 it would suggest that you’re underweight and you may need to put some on. Your doctor will be able to provide more advice.

BMI of 18.5 to 24.9

If your BMI is between 18.5 and 24.9 it suggests that you are a normal or healthy weight for your height. It’s obviously advisable to try and maintain this healthy weight and by doing so you may lower your risk of developing serious health conditions.

BMI of 25 to 29.9

If your BMI value is between 25 and 29.9 this indicates that you are overweight. It’s recommended that you talk to your doctor as they may advise you to lose some weight for health reasons.

BMI of 30 and above

A BMI of 30 or above is categorised as obese and indicates that you are heavily overweight. It’s recommended that you speak with your doctor as your health may be at risk if you do not lose weight.

The BMI calculator details the BMI weight categories and their corresponding BMI scores and can be used as a useful reference point.

Find your nearest hospital that provides Weight Loss Treatments

or use my current location

Feel in control...

...with flexible payment options to suit you:

0% Payment Plans

Spread the cost of your treatment with fixed, monthly payments over a time period to suit you.


Private Medical Insurance

Use your private medical insurance to fund your treatment through our simple referral process.


Self-funding Patients

We offer an alternative range of ways to pay, so you can choose which one best suits you and your finances.


Weight Loss Blog

Keep up to date with the latest Ramsay Health Care weight loss blogs

How to have a Healthy BBQ, PLUS a non-alcoholic, low sugar PIMMS Recipie.

Our Specialist Dietitian, Nichola Ludlam-Raine, shares some tips on how to keep healthy during the summer BBQ season.

Continue Reading

How to Avoid a Fad Diet

Our Specialist Dietitian, Nichola Ludlam-Raine, shares some tips to help avoid falling into a fad diet trap!

Continue Reading

What is Bariatric Surgery?

Learn more about bariatric surgery means, including what it means, the different types of surgery available and who would qualify for this type of procedure.

Continue Reading

Long Term Dietary Advice for Weight Loss & Bariatric Success

Our Specialist Dietitian, Nichola Ludlam-Raine, shares some top tips for achieving and maintaining your weight loss goals through a high protein, low fat, calorie-controlled diet following bariatric surgery.

Continue Reading

Paying for yourself?

Get in touch

Need some advice on a treatment price or booking an initial appointment?

We're here to help.

Or send us a message...