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BMI calculator for adults

Body mass index compares weight with height squared. Health organizations use it to group adult weight for screening. It does not measure body fat, and it does not diagnose a condition.

Enter metric or imperial measures. Imperial values are converted with the exact inch and pound definitions, then the same metric formula is used.

Required fields are marked with *.

Use a comma or a dot for the decimal, as in 12.5 or 12,5. Type thousands as 1000 or 1 000. A single comma or dot is the decimal mark, so 1,000 means 1.

Units

Use 0 to 11.9. Twelve inches is another foot.

Results

The result will appear here.

How to use this calculator

  1. Choose metric or imperial units.
  2. Enter height and weight for an adult.
  3. Read the index and the range beside it. The note under the result is part of the answer.

Formula

The metric formula divides weight in kilograms by height in meters squared.

BMI = kg / m²

The familiar US factor 703 is the same conversion, rounded. This page uses 1 inch = 2.54 cm and 1 pound = 0.45359237 kg, then the metric formula.

  • Below 18.5: underweight
  • 18.5 up to, but not including, 25: the WHO healthy-weight range for screening
  • 25 up to, but not including, 30: overweight
  • 30 or more: obesity

A displayed 24.9 can still sit in the healthy-weight range, because the cut point used here is 25, not 24.9. The categories are for adults. They are not adjusted for children, pregnancy, or athletic muscle.

Worked example

175 cm and 70 kg

Height in meters is 1.75. Square that height: 1.75 × 1.75 = 3.0625.

Divide 70 by 3.0625. The index is about 22.9, which is inside the 18.5 to 25 screening range.

BMI is about 22.9, in the healthy-weight screening range.

Questions

Does a BMI in the healthy-weight range mean someone is well?

No. It is only a ratio of weight to height. Blood pressure, lab results, symptoms, and a clinician’s exam are separate questions.

Why are children not included?

Child BMI is compared with age-specific charts. An adult cut point would mislabel a growing child, so this page does not offer that calculation.

Which units should I trust if both are filled in?

The page uses the unit system that is selected. The other fields are ignored.

Sources

Last reviewed November 1, 2026