BMI Calculator

Body Mass Index from height and weight, with CDC/WHO category labels. Metric and imperial inputs both supported.

Units

Height (feet)

Height (inches)

Weight (lb)

BMI is a population-level screening tool. It doesn't distinguish muscle from fat, so muscular people often score in the “overweight” category despite low body fat, and older adults with low muscle mass may score “normal” despite excess body fat. BMI is not diagnostic.

Your BMI

Category Reference

CDC/WHO BMI categories (adults)

Below 18.5: Underweight
18.5–24.9: Healthy weight
25.0–29.9: Overweight
30.0–34.9: Obesity class I
35.0–39.9: Obesity class II
40.0+: Obesity class III (severe)

Formula: BMI = weight (kg) / height (m)². Imperial: BMI = weight (lb) / height (in)² × 703. Both give the same number.

Real limitations

BMI was designed in the 19th century by Adolphe Quetelet as a population statistic, not an individual health metric. It correlates with body fat at the population level but can be misleading for individuals: athletes with significant muscle mass score high; older adults with sarcopenia (muscle loss) score low despite unhealthy body composition. Better individual metrics include body fat percentage (see the Navy method calculator), waist-to-height ratio, and DEXA scan for clinical accuracy.

BMI cutoffs are also different for children (age- and sex-specific percentiles) and for some ethnic groups — the WHO has proposed lower cutoffs for Asian populations. This calculator uses the standard adult cutoffs; consult a healthcare provider for individualized guidance.