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BMI Calculator

Work out your body mass index, see what it means under the WHO, Korean or Japanese classification, and the normal weight for your height.

Runs locally in your browser – your data is not uploaded

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About the BMI Calculator

Body mass index (BMI) relates your weight to your height: your weight in kilograms divided by your height in metres squared. This calculator works it out from centimetres and kilograms or from feet, inches and pounds, and tells you which weight category it falls into.

Not every country uses the same categories. The World Health Organization counts a BMI of 25 or more as overweight, while the Korean Society for the Study of Obesity starts pre-obesity at 23 and obesity at 25, and the Japan Society for the Study of Obesity starts obesity at 25. Choose the classification you need; Korean and Japanese pages start with their own.

The calculation runs in your browser. Your height and weight are not uploaded or saved.

How to use it

  1. Choose Metric (cm, kg) or US (ft, in, lb).
  2. Enter your height and weight. Decimals are fine.
  3. Read your BMI, its category and where it sits on the scale.
  4. See the normal weight range for your height and how far you are from it.
  5. Switch the classification between WHO, Korea (KSSO) and Japan (JASSO) to compare.

Features

  • Three classifications: WHO, Korean (KSSO 2022) and Japanese (JASSO) categories, with the right one chosen for your language.
  • Metric and US units: Centimetres and kilograms, or feet, inches and pounds.
  • Normal weight range: The weights that give a normal BMI at your height, and how much to gain or lose to reach them.
  • Visual scale: A coloured scale shows where your BMI sits between the category limits.
  • Private: Nothing is sent anywhere; the numbers stay on your device.

Examples

170 cm and 65 kg

A BMI of 22.5: normal weight under every classification.

170 cm and 70 kg

A BMI of 24.2: normal for the WHO and Japan, but pre-obesity under the Korean classification.

5 ft 9 in and 160 lb

A BMI of 23.6, in the normal range for the WHO.

Limitations and notes

  • BMI is meant for adults. It is not used the same way for children and teenagers, whose growth charts compare them with others of the same age and sex.
  • BMI does not tell muscle from fat, so athletes can come out high; it also does not account for age, sex, body shape or pregnancy.
  • The categories are screening guides, not a diagnosis. Talk to a doctor about your weight and health.
  • Heights from 50 to 272 cm and weights from 2 to 650 kg are accepted.

Frequently asked questions

How is BMI calculated?

Weight in kilograms divided by the square of height in metres. For 70 kg and 1.70 m that is 70 ÷ 2.89 = 24.2.

Why does the Korean classification call a BMI of 24 pre-obesity when the WHO says normal?

Studies found that health risks rise at a lower BMI in East Asian populations, so the Korean society uses 23 for pre-obesity and 25 for obesity instead of the WHO limits of 25 and 30.

What is a healthy BMI?

For the WHO and Japan 18.5 to just under 25; for the Korean classification 18.5 to just under 23.

Is BMI accurate for athletes?

Not always. Muscle weighs more than fat, so a muscular person can have a high BMI without extra body fat.

Is my data stored?

No. The calculation happens in your browser and nothing is saved or uploaded.

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