Endocrinology and metabolism
Body Mass Index (BMI)
Weight classification by height and weight.
Body Mass Index (BMI) calculator
Result
24.2kg/m²
Normal weight
How to use it
- 1
Measure height without shoes. Standing height in cm or convert from metres.
- 2
Weight in kg, morning, after voiding. Standardise measurement conditions for serial monitoring.
- 3
BMI limitations. Does not account for muscle mass, body fat distribution, or ethnicity — waist circumference and body fat % give additional context.
When to use it
- Obesity classification
- WHO: overweight ≥25, obese ≥30. Asian populations: lower thresholds (≥23 overweight, ≥27.5 obese).
- Bariatric surgery eligibility
- NICE: BMI ≥40 OR ≥35 + comorbidity.
- Drug dosing
- Some drugs (e.g., aminoglycosides, heparin, NSAIDs) use adjusted or ideal body weight, not actual.
A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.
At a glance
- Specialty
- Endocrinology and metabolism
- Inputs
- 2
- Type
- Formula
