General

BMI Calculator

Calculate Body Mass Index and determine weight category.

Written for clinicians. If you're a parent or patient, don't act on these numbers — talk to your child's doctor.

Scope: Adult BMI categories. For under-18s, BMI must be read as BMI-for-age percentile/z-score (IAP 5–18 y; WHO <5 y), NOT these adult cut-offs — a child can be obese at a BMI these bands call 'normal'.

Inputs

Field	Unit	Notes
Weight	kg	0–500
Height	cm	50–300

FAQ

What is the BMI Calculator?

Calculate Body Mass Index and determine weight category.

What inputs does the BMI Calculator need?

Weight (kg), Height (cm).

Are there any limitations?

Adult BMI categories. For under-18s, BMI must be read as BMI-for-age percentile/z-score (IAP 5–18 y; WHO <5 y), NOT these adult cut-offs — a child can be obese at a BMI these bands call 'normal'.

Related guides

Pediatric BMI-for-Age: Z-Scores and WHO Cutoffs Explained

Why pediatric BMI must be read as BMI-for-age z-scores, not adult thresholds — WHO cutoffs for thinness, overweight and obesity, a worked example, and caveats.

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