Body Mass Index (BMI) Calculator
Enter your height and weight to calculate your BMI
BMI Categories
| Underweight | BMI less than 18.5 |
| Normal weight | BMI 18.5 - 24.9 |
| Overweight | BMI 25 - 29.9 |
| Obese | BMI 30 or greater |
Understanding Body Mass Index (BMI)
What is BMI?
Body Mass Index (BMI) is a simple calculation using a person's height and weight to estimate body fat and assess whether they are at a healthy weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and has become a widely used screening tool in healthcare.
BMI Formulas
Metric Formula
BMI = weight (kg) / height² (m²)
Example: A person weighing 70 kg and 1.75 m tall
BMI = 70 / (1.75 × 1.75) = 22.86
Imperial Formula
BMI = (weight (lbs) / height² (inches²)) × 703
Example: A person weighing 154 lbs and 69 inches tall
BMI = (154 / (69 × 69)) × 703 = 22.76
Detailed BMI Categories
| Category | BMI Range | Health Risk |
|---|---|---|
| Severe Underweight | Below 16.0 | Increased health risks |
| Underweight | 16.0 - 18.4 | Possible health risks |
| Normal Weight | 18.5 - 24.9 | Lowest health risk |
| Overweight | 25.0 - 29.9 | Increased health risks |
| Obese Class I | 30.0 - 34.9 | Moderate health risks |
| Obese Class II | 35.0 - 39.9 | Severe health risks |
| Obese Class III | 40.0 and above | Very severe health risks |
Why BMI Matters
BMI is used by healthcare professionals as a quick screening tool to identify potential weight-related health issues. Research has shown correlations between BMI ranges and risks for various conditions including:
- Type 2 diabetes
- Heart disease and stroke
- High blood pressure
- Certain types of cancer
- Osteoarthritis
- Sleep apnea
- Fatty liver disease
Limitations of BMI
While BMI is a useful screening tool, it has important limitations:
- Doesn't distinguish between muscle and fat: Athletes and bodybuilders may have high BMI due to muscle mass
- Doesn't account for fat distribution: Where you carry fat matters for health
- Varies by age and sex: Older adults and women naturally have more body fat
- Different standards for different ethnicities: Asian populations may have higher health risks at lower BMIs
- Not suitable for everyone: Not accurate for pregnant women, children, or very elderly individuals
Beyond BMI: Other Health Indicators
For a complete health assessment, consider these additional measurements:
- Waist Circumference: Measures abdominal fat, a key risk factor
- Waist-to-Hip Ratio: Indicates fat distribution patterns
- Body Fat Percentage: More accurate measure of actual fat vs. lean mass
- Blood Pressure: Important cardiovascular health indicator
- Cholesterol Levels: Assesses heart disease risk
- Blood Sugar Levels: Screens for diabetes risk
Frequently Asked Questions
Q: Is BMI the same for men and women?
A: The BMI calculation formula is the same for both sexes, but women naturally have a higher percentage of body fat than men. Some health professionals adjust interpretation based on sex.
Q: Can BMI be used for children?
A: BMI can be used for children, but it's interpreted differently using age and sex-specific percentile charts (BMI-for-age). Use our BMI for Age Calculator for children and teens.
Q: What should I do if my BMI is outside the normal range?
A: If your BMI suggests you're underweight or overweight, consult with a healthcare provider. They can perform additional tests and provide personalized recommendations. BMI is just a screening tool, not a diagnostic tool.
Q: How often should I check my BMI?
A: For adults at a healthy weight, checking BMI annually is sufficient. If you're actively working on weight loss or gain, monthly checks can help track progress. Always focus on overall health, not just the number.
Medical Disclaimer
This BMI calculator is for informational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for personalized health recommendations and before making significant lifestyle changes.