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BMI Calculator

Calculate your Body Mass Index in metric or imperial units, with the result placed on the standard WHO category scale.

Runs on your device — nothing is uploaded

Calculate Body Mass Index from height and weight, in metric or imperial, and see where it falls on the standard scale.

How to use this tool

  1. Choose metric or imperial.
  2. Enter your height and weight.
  3. Your BMI, its category, and its position on the scale appear below.

The categories

These are the World Health Organization thresholds for adults:

| BMI | Category | |---|---| | Below 18.5 | Underweight | | 18.5 – 24.9 | Healthy weight | | 25.0 – 29.9 | Overweight | | 30.0 and above | Obese |

What BMI actually measures — and what it misses

BMI is weight divided by height squared. It was designed in the 1830s as a population statistic, not a clinical diagnosis, and it is still useful for that: tracking trends across large groups cheaply.

For an individual, it has real limitations:

  • It cannot tell muscle from fat. Athletes and heavily muscled people routinely score "overweight" or "obese" while carrying very little fat.
  • It ignores fat distribution. Visceral fat around the organs carries far more health risk than fat elsewhere, and BMI cannot see the difference. Waist circumference and waist-to-height ratio are better single indicators.
  • The thresholds are not universal. Health risk rises at lower BMI values in South Asian and East Asian populations, and several countries use lower cut-offs accordingly.
  • It does not apply to children, pregnant people, or the very elderly. Children are assessed on age-and-sex percentile charts instead.

Treat a BMI number as one rough signal among several — not a verdict. If you are concerned about your weight or health, speak to a doctor, who can look at body composition, blood work, family history, and lifestyle together.

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FAQ

Is my height and weight stored?

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

What is the formula?

Metric: weight in kg ÷ (height in metres)². Imperial: weight in pounds ÷ (height in inches)² × 703.

I am muscular and my BMI says obese — is that right?

BMI cannot distinguish muscle from fat, so this is a well-known false positive for athletes and anyone who lifts seriously. Body fat percentage or a waist measurement will be more informative.

Is there a better measure?

Waist-to-height ratio is a strong, easy alternative — keeping your waist under half your height is a widely used rule of thumb. Body fat percentage measured properly is better still.

Does BMI work for children?

No. Children are assessed using age- and sex-specific percentile charts, because healthy body composition changes throughout growth.

Is this medical advice?

No. It is a calculator. Any decision about your health should involve a qualified clinician.

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