How to Calculate Your BMI

Calculating your Body Mass Index (BMI) is simple. Enter your height and weight into our BMI Calculator below to instantly calculate your BMI and see whether your weight falls within a healthy range.

BMI is calculated using the following formula:

BMI = Weight (kg) ÷ Height (m)²

For example, if you weigh 70 kg and are 1.75 m tall:

BMI = 70 ÷ (1.75 × 1.75) = 22.9

You can also use our BMI Calculator below to calculate your result automatically.

BMI Calculator

UK Adult BMI Classification

Once you’ve calculated your BMI, use the table below to understand what your result means.

BMI	Weight Category
Below 18.5	Underweight
18.5–24.9	Healthy Weight
25.0–29.9	Overweight
30.0–34.9	Obesity (Class I)
35.0–39.9	Obesity (Class II)
40.0 and above	Obesity (Class III)

Please note: These BMI classifications apply to most adults. BMI is a useful screening tool but does not directly measure body fat or overall health. Factors such as muscle mass, age, ethnicity and certain medical conditions may also influence your health assessment.

What Does Your BMI Result Mean?

Underweight (Below 18.5)

A BMI below 18.5 is considered underweight. Being underweight may increase your risk of nutritional deficiencies, weakened immunity and osteoporosis. If your BMI is below the healthy range, it’s important to speak with a healthcare professional to identify any underlying causes.

Healthy Weight (18.5–24.9)

A BMI between 18.5 and 24.9 is considered a healthy weight for most adults. Maintaining a healthy weight through a balanced diet and regular physical activity can help reduce the risk of many long-term health conditions.

Overweight (25.0–29.9)

A BMI between 25.0 and 29.9 is classified as overweight. Carrying excess weight may increase your risk of conditions such as high blood pressure, type 2 diabetes and heart disease. Making healthy lifestyle changes can help improve your overall health.

Obesity (30.0 and Above)

A BMI of 30 or above is classified as obesity. Living with obesity can increase the risk of several serious health conditions, including cardiovascular disease, sleep apnoea and certain types of cancer. If you have a BMI of 30 or above, you may benefit from additional support through a clinically supervised Weight Management Programme.

Health Risks Associated with Your BMI

Maintaining a healthy weight is important for your overall health and wellbeing. While BMI is only one measure of health, being underweight, overweight or living with obesity may increase the risk of certain medical conditions.

Health Risks of Being Underweight

Being underweight may increase your risk of:

• Nutritional deficiencies
• Weakened immune system
• Osteoporosis and reduced bone strength
• Fertility problems
• Fatigue and low energy levels

Health Risks of Being Overweight

Carrying excess weight may increase your risk of:

• High blood pressure
• High cholesterol
• Type 2 diabetes
• Heart disease
• Joint pain
• Stroke

Health Risks of Living with Obesity

Living with obesity can significantly increase the risk of several long-term health conditions, including:

• Type 2 diabetes
• Cardiovascular disease
• Sleep apnoea
• Fatty liver disease
• Osteoarthritis
• Certain types of cancer

If your BMI indicates that you are overweight or living with obesity, making positive lifestyle changes and seeking professional support can help improve your overall health and reduce your risk of future health complications.

What Are the Limitations of BMI?

While Body Mass Index (BMI) is a useful screening tool, it does not directly measure body fat or provide a complete picture of your overall health.

For example, BMI does not take into account:

• Muscle mass
• Age
• Sex
• Ethnicity
• Body fat distribution

This means that some people, such as athletes or those with a high level of muscle mass, may have a higher BMI without having excess body fat.

BMI should be used as a guide rather than a diagnosis. Healthcare professionals may also consider other factors, such as your medical history, waist circumference, blood pressure and blood test results, when assessing your overall health and determining the most appropriate treatment or weight management plan.

Looking for a More Detailed Body Composition Assessment?

While BMI is a useful starting point, it cannot distinguish between muscle, fat and bone mass. If you’re looking for a more comprehensive understanding of your body composition, a DEXA (Dual-Energy X-ray Absorptiometry) scan can provide detailed insights beyond BMI alone.

A DEXA scan can measure:

• Body fat percentage
• Muscle mass
• Bone density
• Fat distribution throughout the body

This information can help provide a more accurate picture of your overall health and support personalised weight management goals.

To learn more about our DEXA Scan service or to book an appointment, please contact the PillBox Chemists team.

 

Can Your BMI Determine If You’re Eligible for Weight Loss Medication?

Your BMI (Body Mass Index) is one of the factors healthcare professionals consider when assessing whether you may be suitable for prescription weight loss medication, such as Wegovy® (semaglutide) or Mounjaro® (tirzepatide).

In general, weight loss medication may be considered for adults who:

• Have a BMI of 30 or above, or
• Have a BMI of 27 or above with weight-related health conditions, such as high blood pressure, type 2 diabetes, high cholesterol or sleep apnoea.

However, BMI alone does not determine eligibility. Your healthcare professional will also consider your medical history, current medications, overall health, previous weight loss attempts and, where appropriate, blood test results before recommending treatment.

At PillBox Chemists, our clinically supervised Weight Management Programme includes a consultation, health assessment and blood testing to help determine whether Wegovy®, Mounjaro® or another treatment approach may be suitable for you.

Please note: Wegovy® and Mounjaro® are prescription-only medicines. Treatment is only provided following a clinical assessment and when considered safe and appropriate by a qualified healthcare professional.

How PillBox Chemists Can Help

If you’re looking for professional support with your weight management journey, the team at PillBox Chemists is here to help.

Our clinically supervised Weight Management Programme is designed to provide personalised care, helping you achieve sustainable weight loss safely and effectively.

Our programme includes:

• Initial weight management consultation
• Comprehensive health assessment
• Mandatory blood tests before starting treatment to assess your overall health and ensure treatment is safe and appropriate
• Personalised treatment recommendations
• Access to prescription weight loss medications, including Wegovy® and Mounjaro®, where clinically appropriate
• Ongoing reviews and clinical monitoring
• Lifestyle and nutritional support throughout your journey

Please note that blood tests form an essential part of our programme and are charged separately from the cost of your weight loss medication. This allows our healthcare professionals to assess your health before treatment begins and monitor your progress throughout your weight management journey.

Whether you’re just starting your weight loss journey or looking for additional support, our experienced healthcare team will work with you to develop a treatment plan tailored to your individual needs.

Book a consultation today to learn more about our Weight Management Programme and find out whether prescription weight loss treatment may be suitable for you.

Frequently Asked Questions

What is a healthy BMI?

For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight. Maintaining a healthy BMI can help reduce the risk of conditions such as heart disease, type 2 diabetes and high blood pressure.

How do I calculate my BMI?

You can calculate your Body Mass Index (BMI) by dividing your weight in kilograms (kg) by your height in metres (m), squared. The easiest way is to use our free BMI Calculator above.

Is BMI an accurate measure of health?

BMI is a useful screening tool, but it does not directly measure body fat or overall health. Healthcare professionals may also consider factors such as muscle mass, waist circumference, medical history and blood test results.

What BMI do I need to qualify for weight loss medication?

Prescription weight loss medication may be considered for adults with a BMI of 30 or above, or a BMI of 27 or above if they have weight-related health conditions, such as high blood pressure or type 2 diabetes. Treatment suitability is always determined following a clinical assessment.

Can I get Wegovy® or Mounjaro® if my BMI is below 30?

Some patients with a BMI of 27 or above and certain weight-related health conditions may be suitable for treatment. Your eligibility will depend on your overall health, medical history and assessment by a qualified healthcare professional.

Is BMI the only thing considered before starting weight loss treatment?

No. While BMI is an important factor, healthcare professionals will also consider your medical history, current medications, lifestyle, previous weight loss attempts and blood test results before recommending treatment.

Why do I need a blood test before starting treatment?

At PillBox Chemists, all patients are required to complete a blood test before starting our Weight Management Programme. This helps assess your overall health and ensures that treatment is safe and appropriate. Follow-up blood tests are also carried out every three months to monitor your progress and ongoing health.

Can I improve my BMI?

Yes. Many people can improve their BMI through a combination of healthy eating, regular physical activity and long-term lifestyle changes. For suitable patients, a clinically supervised Weight Management Programme may also include prescription weight loss medication alongside ongoing support.

Does losing weight improve my health?

For many people, losing weight can help reduce the risk of health conditions such as type 2 diabetes, high blood pressure, high cholesterol, heart disease and sleep apnoea. Even modest, sustainable weight loss can have significant health benefits.

How can PillBox Chemists help with weight management?

PillBox Chemists offers a clinically supervised Weight Management Programme, including a consultation, comprehensive health assessment, mandatory blood tests, ongoing clinical monitoring and access to prescription weight loss treatments such as Wegovy® and Mounjaro®, where clinically appropriate.

Ready to Take the Next Step?

Your BMI is just one part of understanding your overall health. Whether you’re looking to lose weight, improve your wellbeing or explore your treatment options, our experienced healthcare team is here to support you.

At PillBox Chemists, we’ll take the time to understand your health, discuss your goals and create a personalised weight management plan that’s right for you.

Book your Weight Management Consultation today and find out whether our clinically supervised Weight Management Programme, including Wegovy® and Mounjaro®, may be suitable for you.

Useful Links:

• Book a Weight Management Consultation
• Learn More About Our Weight Management Programme
• Contact Your Local PillBox Chemists