BMI Calculator

The BMI Calculator computes your Body Mass Index — a simple screening measure that relates weight to height. Enter your weight and height in either metric (kg, cm) or imperial (lbs, inches) units and the tool returns your BMI along with the WHO category: underweight (below 18.5), normal (18.5–24.9), overweight (25.0–29.9), or obese class I, II, or III (30.0 and above). BMI = weight (kg) ÷ height (m)². Imperial: BMI = (weight in lbs × 703) ÷ (height in inches)². The formula is intentionally simple because BMI is designed as a first-pass population-level screening tool, not a full clinical assessment of individual health. It correlates well with body fat percentage in most people but has important limitations that matter when interpreting your own number. Where BMI misleads. It doesn't distinguish between muscle and fat, so muscular athletes routinely score "overweight" or "obese" despite very low body-fat percentages. It doesn't account for bone density, body-frame size, or where fat is distributed on the body — visceral (abdominal) fat is much more health-relevant than subcutaneous fat but BMI ignores the distinction entirely. It uses adult cutoffs, so children and adolescents need age- and sex-adjusted percentile charts instead. And it slightly overestimates health risk in older adults, where a BMI of 25–27 is often associated with better outcomes than lower values. Ethnic differences also matter. Research from the Indian Council of Medical Research and the WHO suggests that South Asians tend to accumulate more visceral fat at lower BMI values, so a lower "overweight" threshold of 23 (rather than 25) is often used for Indian populations, with obesity starting at 25 instead of 30. If you're of South Asian descent, treat a BMI of 24 as a clearer warning sign than the standard WHO chart suggests. Use BMI as a starting point, not a verdict. If your number falls outside the normal range, complement it with other measurements: waist circumference (a strong predictor of cardiovascular risk on its own — under 90 cm for Indian men and under 80 cm for Indian women), waist-to-hip ratio, body-fat percentage from a reliable calliper or DEXA scan, and standard blood tests. A healthcare professional can interpret the combined picture far better than any single number. Everything runs client-side — no measurements are uploaded or logged. Combine this tool with the Calorie Calculator to plan a maintenance, cutting, or bulking diet, and the Age Calculator if you're tracking metrics for children or seniors where age-specific charts matter.