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Home / Weight Loss / How can I calculate my BMI?

How to calculate BMI

Use our calculator to work out your BMI and find out if you’re within a healthy range

What is BMI?

BMI (body mass index) is a calculation that works out if you are a healthy weight or not.

It is important to know your BMI - it lets you know if you’re at risk of health conditions that affect people with too much or too little body fat.

 A person standing on scales next to a tape measure

Doctors and medical professionals often refer to their patient’s BMI as it is usually accurate, as well as cheap and easy to figure out.

If your BMI is too high, you should make it a priority to try to lose weight)

What is my BMI?

The BMI formula

You only need to know two measurements to calculate your BMI:

  • your height
  • your weight
a piece of equipment used to measure someone’s height

If you don’t have the resources to measure yourself at home, you can visit your local GP to get access to a scale and stadiometer (a piece of equipment that accurately measures your height).

This can be in metric units (metres and kilograms) or imperial units (inches and pounds).

You can work out your BMI by using this formula:

BMI = Weight (kg)
(height2)

For example, if you are 1.78m tall and weigh 75kg, your BMI would be 23.7.

Or if you choose to use imperial units, remember to calculate your BMI using pounds (for weight) and inches (for height).

Please note: This formula applies to both genders. A BMI calculator for women will work exactly the same as it does for men.

BMI calculator

Alternatively, you can use our BMI calculator to find out your Body Mass Index quickly and easily.

What about my child’s BMI?

You might be interested to know if your child is at a healthy weight.

Whilst children’s BMIs are calculated using the same formula as adults, the results are interpreted slightly differently.

Children grow at different rates, so instead of having different ranges (underweight, healthy weight and so on), their height and weight are compared with other children of the same age.

If your child’s BMI is within the 5th-85th percentile of other children of the same age, then they will be deemed a healthy weight.

What does my BMI mean?

Body Mass Index has a range from 18.5 up to 35. The lowest number is severely underweight, and the highest number is severely obese.

If you are a healthy weight, your BMI will be between 19 and 25.

Graphic illustrating BMI range

BMI ranges are as follows:

BMI score Weight range
Less than 18.5 Underweight
18.5-24.9 Normal (healthy) weight
25-29.9 Overweight
30-34.9 Obese
More than 35 Severely obese

BMI chart

Below is a Body Mass Index chart. It shows the different weight ranges depending on your height and weight.

A body mass index chart

You can also find your height and weight along the vertical and horizontal lines of the BMI chart to determine if you are a healthy weight.

What are my next steps?

Once you’ve used the BMI calculator to work out your BMI, you should consider your next steps (depending on your score).

The risks of being underweight

If your BMI says you are underweight, it is important to gain some body fat. Being thinner than you should can lead to:

  • malnutrition
  • weak bones
  • a lowered immune system
an underweight woman measuring her waist

If the BMI calculator produced a score of less than 18.5, but you don’t think you’re underweight, ask the opinion of a medical professional. Your BMI could be naturally low due to having a high metabolism and slender frame.

The risks of being overweight or obese

If your BMI says you’re overweight or obese, you should consider losing weight. Having an unhealthy amount of body fat can lead to serious diseases in the long term.

Some health effects of being overweight or obese include:

  • high blood pressure
  • type 2 diabetes
  • coronary heart disease
  • stroke
  • multiple types of cancer
  • mental illness.

Losing weight can be challenging, especially if you don’t know how to start. The first step is often to control your food intake, as well as find out how many calories you should eat to put yourself into a calorie deficit.

Combining a calorie deficit (burning more calories than you consume) with moderate exercise is an effective way to lose weight.

Remember, healthy weight loss is a slow and steady process. Trying to lose weight fast by over-exercising and doing crash diets is unsustainable, and is unlikely to give you the long-term results you’re looking for.

My BMI is within a healthy range

If your BMI score is within a healthy range, then you should aim to stay at your current weight.

Continue eating a balanced diet and exercising a few times a week in order to maintain a healthy lifestyle.

BMI limitations: is my score accurate?

In general, your Body Mass Index is an accurate formula to find out if you are overweight or underweight.

However, it does not take into account the difference between body fat and muscle. If you are an athlete, or you have built muscle through weight training, your BMI might tell you you’re overweight when you are not.

This is because building muscle increases your body weight, without increasing much of your body fat.

If you think your muscle mass might give you an inaccurate BMI reading, you can find out your body fat percentage instead. This reading can tell you if you have too much body fat or not.

Ethnic differences

It has recently been discovered that different races may have different BMI thresholds.

The BMI ranges were initially determined using data based on mostly white populations. Because whites have larger frames than other ethnicities in general, this limits the accuracy of your BMI reading if you aren’t white.

People with an Asian, Middle Eastern, or African/African-Caribbean family background are at risk of health problems at a lower BMI. This means you could be deemed a ‘healthy’ weight, when in reality, you are overweight for your frame.

Consult a doctor if you aren’t sure about the accuracy of your BMI reading.

Why waist size also matters

Alternatively, you can try measuring your waistline to gauge if you are a healthy weight.

 A doctor measuring an overweight patient’s waistline

Your waist measurement is a good way of telling how much fat you have around your middle. A large waist measurement can mean you have too much fat around your vital organs, which can lead to many health conditions.

A general rule is that to be deemed a healthy weight, your waist should be less than half your height.

If you’re 5’4 (64 inches), your waistline should be 32 inches or less.

When should I seek professional help?

If the BMI calculator gave you a score of 30 or above, you might benefit from seeking help from a medical professional.

A doctor might give you a prescription for some weight loss medicine, or, if your BMI is as high as 40 they could point you in the direction of possible weight loss surgeries.

Some effective weight loss treatments include Saxenda, Mysimba, Xenical and Wegovy. Depending on your preferences, you can choose to take oral tablets or use an injectable pen.

You can purchase prescription weight loss treatments online at euroClinix. Simply fill out an online consultation form to be approved by one of our doctors. If you’re suitable for treatment, it will be delivered straight to your door with free next-day delivery.

Want to start your weight loss journey?

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Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 23-09-2023
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