How to Calculate BMI Correctly

June 20, 2026 • 6 min read

Body Mass Index (BMI) is a simple screening tool used to categorize people based on their weight relative to their height. While it's not perfect, it's a good starting point for understanding your weight status.

The BMI Formula

Metric: BMI = weight (kg) / [height (m)]²
US Units: BMI = [weight (lbs) / height (inches)²] × 703

BMI Categories

• Under 18.5 — Underweight
• 18.5 – 24.9 — Normal weight
• 25.0 – 29.9 — Overweight
• 30.0 and above — Obese

Limitations of BMI

• Doesn't distinguish between muscle and fat
• Not accurate for athletes or very muscular people
• Doesn't account for age, sex, or ethnicity differences
• Waist circumference and body composition are often better indicators

Best Practices

• Use our BMI calculator for quick, accurate results
• Track trends over time rather than single readings
• Consult a doctor for personalized health advice