BMI Calculator for Adults

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What is BMI?

BMI, also known as body mass index, serves as a method to assess if your weight aligns with your height and indicates whether you are within a healthy range.

By calculating your BMI, you can determine if you have a healthy weight relative to your height, and it can also indicate whether you are overweight or underweight. While BMI has its limitations, as there are other factors to consider in relation to weight (refer to the limitations information below), it can still provide a helpful guideline.

To discover your BMI and ascertain if you have a healthy weight, simply input your details into our calculator.

Limitations of BMI

Although, in general, BMI is a useful measure of whether or not you’re a healthy weight, it isn’t suitable for everyone. There are some groups of people where a BMI result should be considered carefully, or where it may not even be helpful to use at all.

  • Girls and boys develop differently and have different amounts of body fat at different ages. Therefore, a child’s age and sex are taken into account when looking at their BMI.
  • As we age, we tend to have more body fat and less muscle, so BMI may underestimate body fat in older people.
  • Athletes and people with a lot of muscle may have a high BMI but actually not have much body fat.
  • Pregnant women gain weight as a result of their developing baby. However, it’s still preferable to have a healthy BMI before becoming pregnant to reduce health risks to both you and your developing baby.
  • People from certain Black and Asian backgrounds are at risk of certain health problems at a lower BMI than others. Speak to your GP or practice nurse for more information.


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  • Obesity: identification, assessment and management. National Institute for Health & Care Excellence., published 27 November 2014
  • Healthy Eating: Food Fact Sheet. British Dietetic Association., updated August 2020
  • Bone health checklist. The Royal Osteoporosis Society., accessed 09 March 2021
  • Underweight and fertility when planning a pregnancy. Tommy’s., updated 05 June 2018
  • Healthy snacks: Food Fact Sheet. British Dietetic Association., updated September 2018
  • Help and Treatment. Beat., last updated December 2020
  • Health matters: obesity and the food environment. Public Health England., published 31 March 2017
  • Macronutrients and energy balance. Oxford Handbook of Nutrition and Dietetics (3rd ed). Oxford Medicine Online., April 2020
  • UK Chief Medical Officers' Physical Activity Guidelines. Department of Health and Social Care., published 7 September 2019
  • Body mass index: Considerations for Practitioners. Centers for Disease Control and Prevention., accessed 09 March 2021
  • Weight management before, during and after pregnancy. National Institute for Health & Care Excellence., published 28 July 2010

The information provided on this website is for general informational purposes only and should not be considered as medical advice. Always consult with your healthcare professional or primary care physician before making any changes to your diet, exercise routine, or health practices. Your doctor is in the best position to evaluate your individual health status and provide personalized recommendations. Remember that every individual is unique, and what may be suitable for one person may not be appropriate for another. Your doctor can assess your specific medical history, current health condition, and any potential contraindications before making any decisions regarding your health. Taking proactive steps to ensure your well-being is essential, and seeking professional medical advice is crucial to make informed choices regarding your health and fitness journey.