What Is BMI and What Does Your Number Mean?
Everything you need to know about Body Mass Index: how it's calculated, what the categories mean, and its limitations.
Results are estimates only and do not replace professional medical advice. Consult a qualified healthcare professional before making changes to your diet or exercise routine.
What Is BMI?
Body Mass Index (BMI) is a numerical value calculated from your height and weight. It's widely used as a screening tool to categorize weight status in adults.
Formula: BMI = weight(kg) ÷ height(m)²
Example: A person weighing 70 kg and standing 1.75 m tall has a BMI of: 70 ÷ (1.75 × 1.75) = 22.9 (Normal weight)
Try our BMI Calculator to find yours instantly.
BMI Categories (WHO Classification)
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (Class I) |
| 35.0 – 39.9 | Obese (Class II) |
| 40.0 and above | Obese (Class III) |
What BMI Doesn't Tell You
BMI has significant limitations:
- It doesn't distinguish fat from muscle. A bodybuilder may have a BMI of 28 (overweight) with very low body fat.
- It doesn't account for fat distribution. Visceral (belly) fat is more dangerous than subcutaneous fat, and BMI can't tell the difference.
- It varies by ethnicity. Some Asian populations face metabolic risks at lower BMI thresholds.
- It's less accurate for older adults, who often have more fat relative to muscle at the same BMI.
A More Complete Picture
Use BMI alongside:
- Waist circumference (risk increases above 88 cm for women, 102 cm for men)
- Body fat percentage — track with our Body Fat Calculator
- Fitness level and blood markers
FAQ
Q: Is a BMI of 25 overweight? A: According to WHO classification, yes — 25–29.9 is the "overweight" range. But this is based on population averages and doesn't reflect individual health perfectly.
Q: What is a healthy BMI for a woman? A: Generally 18.5–24.9. Research suggests women may have a slightly different risk profile than men at the same BMI level.
Q: Can you be healthy with a high BMI? A: Yes. Metabolically healthy obesity exists, and many fit, muscular individuals fall in the "overweight" BMI range. Always consult a healthcare professional for a complete assessment.
This content is for informational purposes only and does not constitute medical advice.
Results are estimates only and do not replace professional medical advice. Consult a qualified healthcare professional before making changes to your diet or exercise routine.
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