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Health calculator guide

Updated 2026-08-23

What a BMI Calculator Can and Cannot Tell You

Body mass index, or BMI, compares weight with height. It is a quick screening measure used in many general health contexts, but it is not a diagnosis and it cannot describe every person’s health or body composition.

Open the BMI calculator

The calculation

For metric inputs, BMI is weight in kilograms divided by height in metres squared. For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of about 22.9. The number is a screening result, not a measure of character, fitness or worth.

Why context matters

  • Muscle mass can make BMI higher without indicating excess body fat.
  • Age, pregnancy, ethnicity, disability, illness and development can affect interpretation.
  • A single measurement does not show changes over time or overall wellbeing.
  • Children and teenagers need age- and sex-specific growth references rather than adult cut-offs.

Use the result as a conversation starter

If the result concerns you, consider discussing it with a healthcare professional who can look at your history, measurements, activity, nutrition and other relevant factors. Do not use a general calculator to diagnose a condition or to make a dangerous eating or exercise change.

Privacy

The values entered into the current calculator are processed in the browser on your device and are not sent to KitLumo. Avoid entering identifying information into a general calculator.

Common questions

Is BMI a medical diagnosis?

No. It is a general screening measure and should be interpreted alongside other information by a healthcare professional when needed.

Can athletes have a high BMI?

Yes. Muscle contributes to weight, so BMI can overestimate body-fat risk for some muscular people.

Can I use adult BMI ranges for a child?

No. Children and teenagers require age- and sex-specific growth references.