BMI Calculator: Understand Your Body Mass Index
Body Mass Index (BMI) is the most widely used health screening metric globally, providing a quick and standardized way to assess whether your weight is appropriate for your height. It is used by doctors, public health agencies, insurance companies, and fitness professionals as a first-line indicator of potential weight-related health risks. Our BMI Calculator gives you an instant result along with a clear, actionable interpretation based on WHO standards.
The BMI Formula
Metric: BMI = Weight (kg) ÷ Height² (m²)
Imperial: BMI = (Weight (lbs) ÷ Height² (in²)) × 703
Example: 70 kg, 1.75 m tall → BMI = 70 ÷ (1.75²) = 70 ÷ 3.0625 ≈ 22.9 (Normal weight)
WHO BMI Categories
- Under 18.5: Underweight — may indicate malnutrition or other conditions
- 18.5–24.9: Normal weight — associated with lowest health risk
- 25.0–29.9: Overweight — increased risk of cardiovascular disease and diabetes
- 30.0–34.9: Obese Class I — moderate health risk
- 35.0–39.9: Obese Class II — high health risk
- 40+: Obese Class III — very high risk, medical intervention often needed
BMI and Asian Populations
Research shows that people of South and East Asian descent develop metabolic complications (type 2 diabetes, cardiovascular disease) at lower BMI values than the general WHO thresholds. Many health organizations now recommend using lower cutoffs for Asian populations: overweight at 23+ and obese at 27.5+. Our calculator notes this distinction for Asian users.
Limitations of BMI
BMI does not differentiate between fat and muscle. Athletes may have a high BMI despite very low body fat. Conversely, "normal weight obesity" — a normal BMI but high fat percentage — is increasingly recognized as a health risk. Age, sex, and fat distribution also matter. Always interpret BMI alongside waist circumference, body fat percentage, blood markers, and physical fitness levels.
How to Use This Calculator
- Select metric or imperial units.
- Enter your weight and height.
- Click Calculate for your BMI and weight category.
For the most accurate results, measure your height without shoes and weigh yourself in the morning before eating.
Conclusion
BMI is a useful but imperfect health screening tool. Use it as a starting point for a broader conversation about your health, not as a definitive diagnosis. Our calculator provides instant results that you can bring to your next doctor's appointment for meaningful discussion about your overall health status and any lifestyle adjustments worth considering.