Free health tool
Enter your height and weight to see your body mass index and where it sits on the World Health Organization adult scale.
Your BMI
Healthy weight
Within the range the WHO classes as healthy for adults.
Where your BMI sits on the WHO scale
Want to keep it there? Our clinicians can help you build habits that hold.
Online GP consultationBMI is a screening measure, not a diagnosis. It cannot tell muscle from fat and is not valid during pregnancy or for under-18s.
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The World Health Organization groups adult BMI into the bands below. They describe a population, not a person: two people with the same BMI can be in very different health.
Under 18.5
18.5 – 24.9
25.0 – 29.9
30.0 – 34.9
35.0 – 39.9
40.0 and over
02
BMI is your weight in kilograms divided by the square of your height in metres. That is the whole formula — there is no age, sex or body-composition term in it.
Worked example: someone 1.75 m tall weighing 78 kg has a BMI of 78 ÷ (1.75 × 1.75) = 25.5, which falls in the overweight band.
Imperial entries are converted first (1 stone = 6.35 kg, 1 inch = 2.54 cm), so the result is identical either way.
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BMI is a screening number, not a diagnosis. It is useful precisely because it is crude — it needs only a tape measure and a scales — but that is also its limit.
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BMI is a starting point, not a plan. These are the consultations our doctors run for the things it flags.
150 leiStruggling to lose weight despite diet and lifestyle changes? Our CMR-registered doctors assess the medical and metabolic factors behind your weight. Video consultation, same-day appointments.
Talk any result through with a registered doctor by video, and get the checks that BMI cannot give you.
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Open calculatorQuestions
For most adults aged 18 to 65, the World Health Organization considers a BMI between 18.5 and 24.9 to be the healthy range. Above 25 is classed as overweight and 30 or above as obesity. These are population thresholds, so a single reading is a prompt to look further, not a verdict.
No. The formula and the adult categories are identical. Women generally carry a higher proportion of body fat than men at the same BMI, which is one of the reasons the number is only a starting point.
The arithmetic is exact — the uncertainty is in what BMI measures. It correlates reasonably well with body fat across a population but can misclassify individuals, particularly athletes, older adults and people with a lot of muscle.
Have your blood pressure, cholesterol and blood glucose checked, and talk to a doctor about a plan you can actually sustain. Weight management that includes medical review works considerably better than dieting alone.
No. The calculation runs entirely in your browser. Nothing you type is sent to our servers or saved.
Clinicians normally use BMI as one of the entry criteria for weight management programmes, usually alongside your medical history and any weight-related conditions. Your doctor will confirm what applies to you.
Yes. BMI is the first-line screening measure in Romanian practice, as it is internationally — read alongside waist circumference, blood pressure and blood tests rather than on its own. A raised BMI prompts further assessment; it is not a diagnosis by itself.
Any medical appointment includes height and weight, and most pharmacies will measure them too. You can also work it out here and bring the number to a consultation — our registered doctors can review it alongside your blood pressure, cholesterol and blood glucose.
Book a video consultation with a registered doctor and get a plan built around your history, not a number.
