Body Mass Index (BMI) uses the same formula for both men and women: weight in kilograms divided by height in meters squared. However, what the number means can differ slightly between males and females because of differences in body composition.
Men and women naturally carry different amounts of body fat and muscle. On average, women have a higher percentage of body fat than men at the same BMI value. This is because women naturally store more fat for hormonal and reproductive functions. Men typically carry more lean muscle mass, which weighs more than fat.
This means a man and a woman with the exact same BMI may have different levels of body fat. The BMI scale does not distinguish between the two, which is one of its known limitations.
| BMI Category | BMI Range |
|---|---|
| Underweight | Less than 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity | 30.0 and above |
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Acceptable | 25–31% | 18–24% |
| Obesity | 32%+ | 25%+ |
As both men and women age, body composition changes. Muscle mass tends to decrease while body fat may increase even if body weight stays the same. This means older adults might have a higher body fat percentage than their BMI suggests.
If your BMI falls outside the normal range, it is a good idea to speak with a healthcare professional. They can assess your overall health using additional measurements such as waist circumference, blood pressure, and cholesterol levels.