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BMI Calculator

One number. A bit of context. Zero judgment. Works in metric and imperial.

BMI Calculator

Enter your height and weight to calculate your Body Mass Index.

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Enter your height and weight above to calculate your BMI.

What Is BMI?

Body Mass Index (BMI) is a numerical value derived from a person's weight and height. It's widely used as a screening tool to categorise weight into ranges associated with different levels of health risk. The calculation is simple: weight in kilograms divided by height in metres squared.

BMI Categories (Adults)

  • Below 18.5 — Underweight
  • 18.5 to 24.9 — Healthy weight
  • 25.0 to 29.9 — Overweight
  • 30.0 and above — Obese

The Limits of BMI

BMI is a population-level screening tool, not a precise health diagnostic. It cannot distinguish between fat mass and muscle mass, which means a highly muscular person may register as overweight or obese despite having low body fat. It also doesn't account for age, sex, ethnicity, or fat distribution — all of which influence health risk independently.

Use your BMI as one data point among many, not as a verdict. Waist circumference, blood pressure, cholesterol, and fitness level all provide important context that BMI alone cannot.

BMI for Children and Teenagers

The adult BMI categories above do not apply to people under 18. For children and teens, BMI is assessed on age- and sex-specific growth charts. This calculator is designed for adults only.

Frequently Asked Questions

According to the World Health Organization, a BMI between 18.5 and 24.9 is considered a healthy weight range for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.
BMI is a useful screening tool but has real limitations. It doesn't account for muscle mass, bone density, age, or fat distribution. A very muscular person may have a high BMI without excess body fat. Always discuss results with a healthcare provider.
BMI = weight (kg) ÷ height (m)². In imperial units: BMI = (weight in pounds × 703) ÷ (height in inches)².
Yes. For children and teenagers under 18, BMI is interpreted using age- and sex-specific growth charts rather than fixed adult categories. This calculator is designed for adults only.

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