BMI Calculator

Body Mass Index (BMI) is a screening measure that estimates whether your weight is in a healthy range for your height. It is calculated as your weight in kilograms divided by the square of your height in metres, and it is one of the most widely used indicators in public health because it needs only two easily measured numbers.

BMI is a screening tool, not a diagnosis. It describes a population-level relationship between weight and height, so it works well for comparing groups but is only a starting point for any individual. Its main limitation is that it does not distinguish muscle from fat: a very muscular or athletic person can register a higher BMI without carrying excess body fat, while someone who has lost muscle may register a "normal" BMI that understates their body-fat level.

Because of that limitation, we show a Body Fat % calculator as a suggested next step. If your BMI lands near a category boundary, or if you train seriously with weights, a circumference- or skinfold-based body-fat estimate usually gives a clearer picture than BMI alone. BMI also does not account for age, sex, or where fat is stored on the body, all of which affect health risk.

BMI is most accurate as a population screen for average, moderately active adults whose body composition is typical for their height. For most people it correctly flags when weight is worth a closer look, and it is quick, free, and requires no equipment.

It is least accurate for people whose body composition sits outside the average: competitive athletes and heavily muscled individuals (who may read high without excess fat), older adults who have lost muscle (who may read "normal" while carrying more fat than the number suggests), pregnant people, and children and teenagers, whose growth requires age- and sex-specific charts rather than the adult formula. If you are in one of these groups, pair BMI with a Body Fat % estimate and your clinician's judgement rather than relying on BMI alone.

Formula. BMI = weight (kg) ÷ height (m)². This is the standard formula published by the World Health Organization and used in clinical and public-health settings worldwide. If you enter your measurements in feet/inches or pounds, the calculator converts them to metric before applying the formula, so the result is identical either way.

Why there are two cutoff scales. In 2004 a WHO Expert Consultation concluded that South Asian, Chinese, Japanese, and other Asian-ancestry populations tend to face increased health risk at lower BMI values than the general global cutoffs assume. HealthCalcNow applies the WHO Asian action points automatically for the India region, with a toggle so you can compare against the global standard. Switching regions changes the classification thresholds, not just the labels — the same BMI can read "normal" globally and "overweight" under the Asian cutoffs.

What "high confidence" means here. BMI is one of the most extensively population-validated screening formulas in public health, which is why we label it high confidence. That reflects the strength of the evidence behind the formula — it is not a claim that BMI is a precise individual diagnostic. Use it to decide whether a closer look is worthwhile, not as a verdict on its own.