BMI Calculator
Calculate Body Mass Index (BMI) with WHO classification. Includes interpretation for adults and clinical considerations.
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Body Mass Index
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About This Calculator
Body Mass Index (BMI) is a measure of body fat based on height and weight. It is widely used as a screening tool for weight categories that may lead to health problems. While BMI has limitations, it remains a useful clinical tool when combined with other assessments.
Formula
BMI = weight (kg) / height (m)²BMI is calculated by dividing weight in kilograms by height in meters squared. For imperial units: BMI = (weight in lbs × 703) / (height in inches)²
Clinical Considerations
- •BMI may overestimate body fat in athletes and muscular individuals
- •BMI may underestimate body fat in older adults who have lost muscle mass
- •Consider waist circumference for additional cardiovascular risk assessment
Limitations
- •Does not differentiate between fat and lean mass
- •Does not indicate body fat distribution
- •May not be accurate for pregnant women
- •Different cut-points may apply for Asian populations
Interpretation Guide
| Range | Classification | Recommendation |
|---|---|---|
| <-18.49 | Underweight | Evaluate for underlying causes; consider nutritional counseling |
| 18.5-24.99 | Normal Weight | Maintain healthy lifestyle; regular physical activity |
| 25-29.99 | Overweight | Lifestyle modifications; assess cardiovascular risk factors |
| 30-34.99 | Obese Class I | Weight management program; screen for obesity-related comorbidities |
| 35-39.99 | Obese Class II | Intensive lifestyle intervention; consider pharmacotherapy |
| 40-+ | Obese Class III | Multidisciplinary approach; consider bariatric surgery evaluation |
Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a numerical value calculated from your weight and height. It provides a simple screening method to categorize weight status and associated health risks. BMI = weight (kg) / height (m)².
What are the limitations of BMI?
BMI does not distinguish between fat and muscle mass, does not account for fat distribution, and may misclassify muscular individuals as overweight. It also may not accurately reflect health risks in older adults, athletes, or certain ethnic groups.
Are BMI ranges different for different populations?
Yes, WHO recommends lower BMI cut-points for Asian populations due to higher cardiovascular risk at lower BMI. Overweight may be defined as BMI ≥23 and obesity as BMI ≥27.5 for Asian populations.
Should BMI be used alone to assess health?
No. BMI should be used alongside other measures such as waist circumference, body composition, blood pressure, lipid profile, and blood glucose to comprehensively assess metabolic health and disease risk.
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. However, optimal BMI may vary based on age, sex, ethnicity, and muscle mass. Consult with a healthcare provider for personalized guidance.
References
1. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004. doi: 10.1016/S0140-6736(03)15268-3
View Source →2. National Heart, Lung, and Blood Institute. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication. 1998
View Source →Last updated: 2024-12-18
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