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BMI Calculator

Enter your height and weight in metric or imperial units to get your body mass index (BMI), the adult category it falls into and the weight range that corresponds to a BMI of 18.5 to 24.9 at your height. BMI is a quick screening number, not a diagnosis, and nothing you enter leaves your browser.

Calculate body mass index

Units
cm
kg

Enter your height and weight to see the BMI.

How to use it

  1. Choose your units

    Metric uses centimetres and kilograms. Imperial uses feet, inches and pounds.

  2. Enter height and weight

    Type your height and weight. In imperial mode, leave inches empty if your height is a whole number of feet.

  3. Read the result

    You get the BMI to one decimal place, the category and the weight range that would give a BMI between 18.5 and 24.9.

Example: 170 cm and 68 kg

Height in metres is 1.70, so the height squared is 2.89. Dividing 68 by 2.89 gives 23.5, which is in the normal weight range. At 170 cm, a BMI of 18.5 to 24.9 corresponds to roughly 53.5 kg to 72.0 kg.

WHO adult BMI categories

The categories below are the adult cut-offs published by the World Health Organization. They are the ones this calculator uses.

BMI ranges and categories for adults
BMI (kg/m²)Category
Below 16.0Severe thinness
16.0 to 16.9Moderate thinness
17.0 to 18.4Mild thinness
18.5 to 24.9Normal weight
25.0 to 29.9Overweight
30.0 to 34.9Obesity class I
35.0 to 39.9Obesity class II
40.0 and aboveObesity class III

Limits and limitations

  • Height must be between 50 and 272 cm and weight between 2 and 650 kg, so that typing errors are caught.
  • The categories are for adults. For children and teenagers, BMI is judged against age and sex charts, which this tool does not use.
  • BMI does not measure body fat or health. Muscular people, older adults, pregnant women and people of different ethnic backgrounds may be misjudged by the standard cut-offs.
  • This is general information, not medical advice. Talk to a doctor or dietitian about your own health and weight.

Frequently asked questions

Is my height and weight stored or sent anywhere?

No. The height and weight you enter is processed by JavaScript running in your browser and is not sent to a server. The page itself still loads from a web server like any website. This site can load advertising or analytics scripts, but only after you accept them in the cookie notice. They are separate from the tools, which never pass the files or text you work with to them.

How is BMI calculated?

Weight in kilograms divided by height in metres squared. In imperial units the pounds and inches are first converted to kilograms and metres, using 1 lb = 0.45359237 kg and 1 in = 2.54 cm.

Is a BMI in the normal range always healthy?

Not necessarily. BMI ignores where fat is carried, muscle mass, fitness and medical history. It is best used as one rough indicator alongside other measures and professional advice.

Why does my category change by a rounding step?

The category uses the BMI rounded to one decimal place, the same figure you see on screen, so a result of 24.96 is shown as 25.0 and counted as overweight.

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