BMI Calculator
Calculate your Body Mass Index with support for all units — metric and imperial — and 4 international standards including Asian-specific thresholds.
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What is BMI?
Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It was devised by Belgian mathematician Adolphe Quetelet in the 1830s and is used as a screening tool to categorize a person's weight relative to their height.
WHO Classification (International)
| BMI | Category |
|---|---|
| < 16.0 | Severely Underweight |
| 16.0–17.0 | Moderately Underweight |
| 17.0–18.5 | Mildly Underweight |
| 18.5–25.0 | Normal Weight |
| 25.0–30.0 | Overweight (Pre-obese) |
| 30.0–35.0 | Obese Class I |
| 35.0–40.0 | Obese Class II |
| ≥ 40.0 | Obese Class III |
Asian Standards (Lower Thresholds)
| BMI | Category (HK) |
|---|---|
| < 18.5 | Underweight |
| 18.5–23.0 | Normal |
| 23.0–25.0 | Overweight I |
| 25.0–30.0 | Overweight II |
| ≥ 30.0 | Obese |
BMI and Gender Differences
While the BMI formula is the same for men and women, body composition differs significantly between sexes at the same BMI value. Women naturally carry more body fat than men at an equivalent BMI.
Male Body Fat Ranges
| Essential fat | 2–5% |
| Athletic | 6–13% |
| Fit | 14–17% |
| Acceptable | 18–24% |
| Obese | 25%+ |
Female Body Fat Ranges
| Essential fat | 10–13% |
| Athletic | 14–20% |
| Fit | 21–24% |
| Acceptable | 25–31% |
| Obese | 32%+ |
This calculator estimates body fat percentage using the Deurenberg formula: %BF = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4
What is BMI Prime?
BMI Prime is the ratio of your BMI to the upper limit of the normal range (25 kg/m²). A BMI Prime of 1.0 means you are at the upper boundary of normal weight.
Frequently Asked Questions
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Medical Disclaimer
This BMI calculator is for informational and educational purposes only. BMI is a screening tool and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for health concerns.