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Calculate your Body Mass Index in seconds by entering your height and weight. Get your BMI score along with a clear classification — underweight, normal, overweight, or obese.
BMI calculator · metric and imperial · BMI category · healthy weight range · age and sex context
Input your height (in cm or feet/inches) and weight (in kg or lbs). Switch between metric and imperial units using the toggle at the top of the tool.
The calculator instantly computes your BMI using the standard formula: weight in kilograms divided by height in metres squared (kg/m²).
Your result is mapped to a WHO classification range: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), or obese (30 and above).
BMI stands for Body Mass Index, a numerical value derived from a person’s weight and height. The formula divides weight in kilograms by the square of height in metres. It was developed in the 19th century by mathematician Adolphe Quetelet as a population-level screening tool. BMI is widely used in clinical settings to identify potential weight-related health risks. It is not a diagnostic tool and does not measure body fat directly.
BMI has known limitations and should not be interpreted in isolation. It does not distinguish between muscle mass and fat mass, meaning athletes or heavily muscled individuals may fall into the “overweight” category despite having low body fat. It also does not account for age-related changes in body composition, sex-based differences in fat distribution, or ethnic variations in risk thresholds. The WHO and many health organisations acknowledge these limitations and recommend using BMI alongside other measures such as waist circumference.
According to standard WHO classification, a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese. Some Asian health guidelines use lower thresholds — for example, a BMI of 23 or above may be considered overweight for certain East Asian populations. Always consult a healthcare provider before drawing health conclusions from your BMI result.
This calculator is designed for adults aged 18 and over. BMI interpretation for children and teenagers works differently — it uses age- and sex-specific percentiles rather than fixed thresholds. For children aged 2–19, a separate BMI-for-age percentile chart is required. Paediatric BMI tools are available through health authority websites such as the CDC and NHS. If you are checking a child’s BMI, please use an age-appropriate tool instead.
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The BMI Calculator is a simple screening tool used to assess whether a person’s weight falls within a healthy range relative to their height. It is widely used by healthcare providers, fitness professionals, and individuals tracking personal health goals. While BMI is not a complete measure of health, it provides a quick reference point that can prompt further investigation when values fall outside normal ranges.
All calculations are performed entirely in your browser; no measurements or personal data are sent to any server.
