BMI Calculator

Body Mass Index (BMI) is a simple height-and-weight ratio used as a population-level screening tool. Enter metric (kg/cm) or imperial (lb/ft-in) measurements to see your BMI and the matching WHO adult category. Everything runs locally in your browser — your inputs are not uploaded to produce the result.

BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²). Imperial inputs are converted first. For most adults, under 18.5 is underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, and 30+ obese, with further subclasses above that. Categories can differ for children and some ethnic groups.

BMI does not measure body fat directly. Athletes and people with high muscle mass can show a higher BMI without excess fat. Older adults and some medical conditions can also make BMI less informative. Waist measurement, fitness, blood markers, and clinical advice give a fuller picture.

Switch between UK and US unit presets if you prefer kilograms and centimetres or pounds and feet/inches. Re-enter values after switching if you need an exact match to a printed chart. Results update as soon as height and weight are valid.

Use BMI Calculator as one data point for general awareness, not a diagnosis. Speak to a GP or qualified health professional before making medical or diet decisions based on BMI alone.