What is BMI?
Body Mass Index (BMI) is a simple screening tool that measures body size based on height and weight. It's calculated as weight in kilograms divided by the square of height in meters (BMI = kg / m²). BMI helps gauge potential health risks like heart disease, stroke, high blood pressure, and high cholesterol. In 2025, with U.S. obesity rates at 42% (CDC data), BMI remains a quick indicator, though not perfect— it overlooks muscle mass, bone density, age, sex, and ethnicity.
Categories:
- Underweight (<18.5): Possible malnutrition, weakened immunity, or illness.
- Normal (18.5–24.9): Healthy range; maintain balanced diet and exercise.
- Overweight (25–29.9): Increased risk of diabetes, hypertension; focus on lifestyle changes.
- Obese (≥30): Higher chances of cardiovascular issues, sleep apnea; seek medical advice.
This calculator uses the standard formula for instant results. Enter height (feet/inches) and weight (kg) for your BMI and category. For lbs, convert (1 kg ≈ 2.2 lbs).
How to Use the BMI Calculator
- Input your height in feet and inches (e.g., 5 ft 6 in).
- Enter weight in kilograms.
- Click "Calculate BMI" for results.
- Review category and tips—recalculate as needed.
Example: 5 ft 3 in (1.60 m), 60 kg → BMI 23.4 (Normal weight).
Understanding Your BMI Results
- Underweight Risks: Anemia, osteoporosis, infertility, higher mortality. Consult a doctor for nutrient deficiencies.
- Normal: Low disease risk; aim for 150 min/week moderate exercise (WHO).
- Overweight/Obese Risks: Type 2 diabetes, certain cancers (breast, colon), joint pain, depression. Gradual weight loss (1-2 lbs/week) via diet/exercise helps.
Limitations of BMI
BMI doesn't differentiate fat from muscle—athletes may score "overweight." It's less accurate for: pregnant women (use pre-pregnancy weight), children (use growth charts), elderly (muscle loss skews low), or bodybuilders. For precise health, pair with waist circumference, blood tests, or DEXA scans. Not a diagnostic—see a doctor for personalized advice.
When to See a Doctor
If BMI <18.5 or >30, or with symptoms like fatigue, joint pain, or unexplained weight changes. Annual check-ups recommended; BMI is a starting point, not the full picture.
Disclaimers
This tool provides estimates only—BMI isn't a health diagnosis. Results vary by factors like ethnicity (e.g., Asian BMI thresholds lower). Not for medical decisions; consult healthcare professionals. Data from CDC/WHO (2025). No liability for outcomes.
Calculate your BMI today for insights.