Limitations of BMI: what the number misses

BMI is popular because it is simple. That simplicity is also why it has limits. Treat the number as a screening hint, not a verdict on your health.

Common limitations

• Does not distinguish fat from muscle or bone
• Can overestimate risk in muscular athletes
• Can underestimate risk in people with low muscle and higher fat
• Body composition differs by age, sex, and ethnicity at the same BMI
• Not appropriate as the sole measure in pregnancy
• Children and teens usually need CDC BMI-for-age percentiles, not adult WHO cutoffs

When to talk to a clinician

If you have concerns about weight, growth, nutrition, or metabolic health - or if a BMI result does not match how you feel - speak with a qualified clinician. Online calculators cannot replace personal medical care.

Still useful as a private, educational check? Run the numbers locally on Jigglify, then read the classification with the limitations in mind.
Open the BMI calculator →