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About Bmi Calculator Online
This tool calculates Body Mass Index (BMI) — a screening number derived from your weight and height. Enter weight and height in metric (kg, cm) or imperial (lb, ft/in) units, and the calculator returns your BMI along with the standard category: underweight (under 18.5), normal (18.5–24.9), overweight (25–29.9), or obese (30+).
BMI is a quick screening tool, not a diagnosis. It does not distinguish muscle from fat, so athletes and bodybuilders often score "overweight" despite being lean. It also doesn't account for body fat distribution, age, or ethnicity. For most adults though, BMI gives a reasonable starting point.
If your BMI is well outside the normal range, the result is worth discussing with a doctor — but BMI alone shouldn't drive major health decisions.
How to use this tool
How to calculate Body Mass Index
Enter weight with its unit
Pick "Weight unit" (kg, g, lb, oz, st, t — stone is a decimal, e.g. 11.5 = 11 st 7 lb) and type the number into "Weight". Anything 0–1,000,000 is accepted by the schema.
Enter height with its unit
Pick "Height unit" (cm, m, mm, in, ft, yd — feet is decimal, e.g. 5.75 ≈ 5 ft 9 in) and type the number into "Height". Mix the systems freely: lb + cm is fine.
Press Run
Result returns bmi (rounded to 2 decimals), category (Underweight / Normal range / Overweight / Obese I-III) with a categoryId, healthyWeightMinKg / MaxKg for the WHO 18.5–25 band, ponderalIndex and bmiPrime.
Read responsibly
Output also includes weightKg, heightM, and the exact units you used. BMI is a screening number, not a diagnosis — athletes, pregnant people, and elderly populations need different reference ranges.