BMI Calculator

Enter your height and weight to get your body mass index and the WHO weight category for adults. This BMI calculator also shows the healthy weight range for your height.

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Your BMI
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For general information. Not medical advice.

How to use the BMI Calculator

  1. Pick Metric or US units.
  2. Enter your Height and Weight. In US units, height takes feet and inches.
  3. Press Calculate. Your BMI appears with its category, a marker on the scale, and the weight range that counts as healthy for your height.

How it works

BMI = weight (kg) ÷ height (m)²
healthy range = 18.5 × height² to 24.9 × height²
  • weight: body weight in kilograms. Pounds are multiplied by 0.4536 first.
  • height: height in metres. Inches are multiplied by 0.0254 first.

WHO adult categories: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and over obese (class I to 34.9, class II to 39.9, class III from 40). BMI Prime is BMI divided by 25, so anything above 1.0 is over the normal range.

Examples

  • 175 cm and 70 kg: 70 ÷ 1.75² = 22.9, normal weight. The healthy range for 175 cm is 56.7 to 76.3 kg.
  • 5 ft 10 in and 200 lb: 1.778 m and 90.7 kg give a BMI of 28.7, overweight.
  • 160 cm and 45 kg: 17.6, underweight.

What BMI can and cannot tell you

BMI is a screening number. It is quick and needs no equipment, which is why doctors and insurers use it for large groups. It only compares weight with height, though, so it cannot see where the weight comes from.

A muscular athlete can land in the overweight range with little body fat. An older adult who has lost muscle can read as normal while carrying more fat than is healthy. For a closer look at body composition, try the body fat calculator, which uses tape measurements instead.

Limitations

  • The categories are for adults aged 20 and over. Children and teens need age- and sex-specific percentiles.
  • BMI does not separate muscle from fat, and it does not apply during pregnancy.
  • Some health bodies use lower cut-offs for people of Asian descent, such as 23 for overweight. This calculator uses the standard WHO values.

Frequently asked questions

What is a healthy BMI?

For adults, a BMI from 18.5 to 24.9 is in the normal range set by the World Health Organization.

How do I calculate BMI by hand?

Divide your weight in kilograms by your height in metres squared. For 70 kg and 1.75 m, that is 70 ÷ 3.0625 = 22.9.

Is BMI accurate for athletes?

Not very. Muscle is dense, so muscular people often score as overweight without extra fat. A body fat measurement tells you more.

Does this BMI calculator work for children?

No. Children and teenagers are assessed with BMI-for-age percentile charts, which this tool does not include.

Often used together with the BMI Calculator.