BMI Calculator Guide: What Your Results Really Mean

BMI is widely used but often misunderstood. Here's what your number really means — and what it doesn't.

What Is BMI and How Is It Calculated?

BMI = weight (kg) / height squared (m2). In imperial: (weight lbs x 703) / height squared (inches2). A 5'9" person weighing 170 lbs has BMI 25.1.

BMI Categories

• Under 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+: Obese Class III

Is BMI Accurate? The Limitations

• Doesn't distinguish muscle from fat (athletes often "overweight")
• Doesn't account for fat distribution (belly fat is more dangerous)
• Not accurate for all ethnicities
• Doesn't consider age or gender

Better Alternatives

Body fat percentage is more accurate. Waist circumference over 40" (men) or 35" (women) indicates higher risk. Consult your doctor for a complete health picture.