Use BMI cutoffs for underweight severity screening and care-escalation conversations.
This calculator applies standard BMI math and highlights low-BMI thresholds often discussed in severe underweight screening contexts.
It is not a diagnostic tool for anorexia nervosa. Diagnosis requires a qualified clinical assessment including behavioral and psychological criteria.
Use recent measured values in consistent units.
Compute kg/m^2 from weight and height.
Compare against underweight severity ranges.
Repeated declines may indicate rising risk.
Include menstruation, labs, vitals, and behaviors.
Seek professional care for concerning results or symptoms.
BMI = weight(kg) / height(m)^2
BMI quantifies weight relative to height. Very low values can flag serious nutritional risk, but diagnosis requires more than BMI.
BMI = 42 / 1.70^2 = 14.53
BMI 14.5 suggests very high medical risk; urgent evaluation is advised
BMI = 47 / 2.8224 = 16.65
BMI 16.7 is underweight and warrants full assessment
BMI drops from 18.0 to 16.5
Rapid decline indicates elevated concern and need for timely care