BMI (Body Mass Index) is calculated as weight in kilograms divided by height in meters squared. It's widely used because it's fast and free — but it's a screening tool, not a diagnosis. Here's how to use it correctly.
BMI Categories
- •Underweight: BMI below 18.5
- •Normal weight: BMI 18.5 – 24.9
- •Overweight: BMI 25 – 29.9
- •Obese Class I: BMI 30 – 34.9
- •Obese Class II: BMI 35 – 39.9
- •Obese Class III: BMI 40 and above
Healthy Weight Range by Height (Imperial)
- •5'0" (60 in): 97 – 128 lbs
- •5'3" (63 in): 107 – 141 lbs
- •5'6" (66 in): 118 – 154 lbs
- •5'9" (69 in): 128 – 168 lbs
- •6'0" (72 in): 140 – 183 lbs
- •6'3" (75 in): 152 – 200 lbs
What BMI Doesn't Tell You
- •Muscle vs. fat: A muscular athlete can have a BMI of 28 (overweight) while having very low body fat
- •Fat distribution: Abdominal (visceral) fat is more dangerous than fat stored in hips/thighs — BMI doesn't distinguish
- •Age and sex: BMI thresholds were developed on European male populations; accuracy varies by ethnicity and sex
- •Better metrics: Waist-to-height ratio (< 0.5 is healthy) and body fat percentage give more complete pictures
BMI is a starting point, not a verdict. Use it alongside waist circumference, body fat %, and metabolic markers (blood pressure, blood glucose, cholesterol) for a complete health picture.
Frequently Asked Questions
What BMI range is considered healthy?
The WHO and CDC classify BMI as: Underweight < 18.5, Normal weight 18.5–24.9, Overweight 25–29.9, Obese ≥ 30. A BMI of 22 is solidly healthy for most adults. However, BMI doesn't distinguish muscle from fat — a muscular athlete may have a 27 BMI without any excess fat.
Check your BMI →How is BMI calculated?
BMI = weight (kg) ÷ height² (m²). In imperial units: BMI = (weight in lbs × 703) ÷ height² (in inches). For a 5'8" person weighing 175 lbs: BMI = (175 × 703) ÷ 68² = 123,025 ÷ 4,624 ≈ 26.6 (overweight range). It's a quick screening tool, not a diagnostic.
How accurate is BMI as a health measure?
BMI correlates with health risks at the population level but is imperfect for individuals. It doesn't account for muscle mass (athletes are often 'overweight'), bone density, fat distribution, age, or ethnicity. Waist circumference and body fat percentage are often more informative alongside BMI for individual health assessment.
Check body fat percentage →What BMI is considered overweight or obese?
Overweight: BMI 25.0–29.9. Class 1 Obesity: 30.0–34.9. Class 2 Obesity: 35.0–39.9. Class 3 (severe) Obesity: 40+. Some Asian populations use lower thresholds (overweight ≥ 23, obese ≥ 27.5) because the same BMI carries higher metabolic risk due to differences in body composition.
Is BMI different for men and women?
The same BMI scale applies to both men and women (18.5–24.9 normal), but at the same BMI, women generally have more body fat than men. A woman with a BMI of 25 typically has 30–35% body fat; a man with the same BMI has 20–25%. This is why body fat percentage calculators give different thresholds by sex.
Calculate your ideal body weight →