BMI Calculator

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This adult BMI calculator estimates body mass index from height and weight. It is a private screening tool, not a diagnosis or a judgement about health, body shape, fitness, or worth.

Adult BMI Calculator

Units

The calculation happens only in your browser. Entered values are not sent to the website, analytics, advertising systems, or the server.

Enter your height and weight to calculate adult BMI.
Important limits: BMI is a broad adult screening measure. It does not directly measure body fat, muscle, waist-to-height ratio, fitness, nutrition, mental health, or individual risk. Children and teenagers need age- and sex-specific assessment. Pregnancy, postpartum health, older age, high muscle mass, some medical conditions, and ethnicity can also change how BMI should be interpreted.
If weighing, measuring, food, exercise, or body checking feels distressing, compulsive, or tied to self-harm urges, it may be better not to keep checking numbers. Please consider speaking with a GP, therapist, dietitian, or another qualified professional. If you might harm yourself or someone else, contact local emergency services or crisis support now.

BMI Questions

What BMI categories does this calculator use?

For adults, the usual categories are below 18.5, 18.5 to 24.9, 25.0 to 29.9, and 30.0 or above. The calculator also shows obesity class ranges when BMI is 30.0 or above. These are screening categories, not diagnoses.

Can BMI tell me whether I am healthy?

No. BMI can be one piece of context, but health assessment may also include waist-to-height ratio, blood pressure, blood tests, symptoms, medical history, medications, eating patterns, activity, sleep, stress, mood, and personal circumstances.

When should I seek professional advice?

Consider speaking with a GP or qualified clinician if weight changes are sudden, unexplained, distressing, linked with eating problems, associated with physical symptoms, or affecting daily life. BMI results and weight-related treatment decisions need individual clinical context.

How to Read the Result

BMI is calculated from weight divided by height squared. It can be useful for broad adult screening, but it is a limited number. It cannot tell you what your body composition is, how healthy you are, or what treatment, if any, would be appropriate.

NICE guidance notes that BMI should be interpreted with caution because it is not a direct measure of central adiposity. Waist-to-height ratio and clinical context may matter, and some ethnic backgrounds have increased cardiometabolic risk at lower BMI thresholds.

Related Mental Health Routes

If weight, body image, anxiety, low mood, stress, or self-criticism is part of what brought you here, the number from a BMI calculator may be less important than getting kind, practical context. You may find the mental health help, anxiety, and depression pages useful.

For the limits of website information, see the disclaimer and how this mental health information is written and reviewed. For personal help, you can contact Dr Jonathan Haverkampf or make an appointment.

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Sources and Review Note

Page created and source checked: 22 May 2026. This page is general health information and a browser-only calculator. It does not provide diagnosis, treatment advice, nutritional advice, or crisis care.

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