About Body Mass Index (BMI)

What is BMI?

BMI is a screening measure that estimates body fat by relating weight to height. It is calculated as weight divided by height squared and categorized to indicate underweight, healthy weight, overweight, or obesity.

Why maintain a healthy BMI?

• Lower risk of type 2 diabetes, hypertension, heart disease, and stroke.
• Better mobility, sleep quality, and energy levels.
• Reduced joint strain and certain cancer risks.

Advantages

• Simple, fast, and inexpensive.
• Useful for population-level screening and trends.

Limitations

• Does not distinguish fat from muscle; athletes may read high.
• Does not show fat distribution; visceral fat risk is not captured.
• Cut-offs can vary by age, sex, and ethnicity; use clinical judgment.

How to manage BMI

• Balanced diet emphasizing whole foods, adequate protein, and portion control.
• Regular activity: at least 150 minutes/week moderate cardio plus 2 days strength training.
• Consistent sleep, stress control, and steady habits over rapid changes.
• Consult a clinician before major changes, especially with medical conditions.

Inputs used in this calculator

• Height: Your stature. Enter in centimeters or meters (or feet/inches if supported). Used to square the height in the BMI formula.
• Weight: Your body mass. Enter in kilograms (or pounds if supported). Used as the numerator.
• Units: Metric or imperial. The tool converts to kg and meters internally.
• Age/Sex (optional): May be displayed for context; BMI formula itself does not use them.

How BMI is calculated

BMI = weight(kg) ÷ [height(m)]²
If using lb/in: BMI = 703 × weight(lb) ÷ [height(in)]²

Interpreting results (Adults)

• < 18.5: Underweight
• 18.5–24.9: Healthy weight
• 25.0–29.9: Overweight
• ≥ 30.0: Obesity (Class I: 30.0–34.9, Class II: 35.0–39.9, Class III: ≥ 40.0)

Note: BMI is a screening tool, not a diagnosis. Body composition, waist circumference, fitness, and medical history provide fuller insight.