What is Body Mass Index (BMI)?
Body Mass Index is a simple calculation that uses your height and weight to estimate the amount of body fat you have. It’s a screening tool that can indicate whether you might be at risk for health problems associated with weight.
BMI was developed in the 1830s by Belgian mathematician Adolphe Quetelet as a simple way to assess whether a person’s weight is appropriate for their height. Today, it remains one of the most commonly used methods for classifying weight status and identifying potential health risks.
BMI Formula
The BMI formula is calculated by dividing your weight in kilograms by your height in meters squared:
BMI = weight (kg) / [height (m)]²
For those using imperial measurements (pounds and inches), the formula is:
BMI = [weight (lbs) / height (inches)²] × 703
Calculate Your BMI
Use our interactive calculator below to determine your BMI. Simply enter your height and weight, then click the calculate button to see your results instantly.
Calculate Your BMI NowNote: This calculator is designed for adults 20 years and older. For children and teens, please use a BMI calculator specifically designed for their age group, as their BMI is interpreted differently.
Understanding BMI Categories
BMI results are typically categorized into four main groups, each associated with different health implications. Understanding your BMI category can help you make informed decisions about your health.
| BMI Category | BMI Range (kg/m²) | Health Risk |
| Underweight | Below 18.5 | Increased risk of nutritional deficiencies and osteoporosis |
| Normal Weight | 18.5 – 24.9 | Lowest risk of health problems |
| Overweight | 25.0 – 29.9 | Increased risk of heart disease, stroke, and type 2 diabetes |
| Obesity (Class I) | 30.0 – 34.9 | High risk of health problems |
| Obesity (Class II) | 35.0 – 39.9 | Very high risk of health problems |
| Obesity (Class III) | 40.0 and above | Extremely high risk of health problems |
Visual representation of different BMI categories
Interpreting Your BMI Results
Underweight (BMI below 18.5)
Being underweight may indicate malnutrition or underlying health conditions. It can lead to a weakened immune system, fragile bones, and fertility issues.
Normal Weight (BMI 18.5-24.9)
A BMI in this range suggests a healthy weight relative to height. Maintaining this range through balanced nutrition and regular physical activity is recommended.
Overweight & Obesity (BMI 25+)
Higher BMI categories are associated with increased risk of heart disease, type 2 diabetes, high blood pressure, and certain cancers. Small improvements can significantly reduce health risks.
“BMI is a useful screening tool, but it does not directly measure body fat or account for muscle mass, bone density, overall body composition, or racial and sex differences.”
Limitations of BMI
While BMI is a valuable screening tool, it has several limitations that are important to understand when interpreting your results.
BMI Strengths
- Easy to calculate and widely accessible
- Correlates with body fat for most people
- Useful for population-level health assessments
- Helps identify potential weight-related health risks
- Consistent measurement across healthcare settings
BMI Limitations
- Doesn’t distinguish between fat, muscle, and bone mass
- May overestimate body fat in athletes and muscular individuals
- May underestimate body fat in older persons and those with muscle loss
- Doesn’t account for differences in body composition across ethnic groups
- Doesn’t indicate fat distribution (central vs. peripheral)
Two individuals can have the same BMI but very different body compositions
Important: BMI should be used as one of several tools to assess health, not as a sole diagnostic measure. Always consult with healthcare professionals for comprehensive health evaluations.
Alternative Measurements to Complement BMI
For a more comprehensive assessment of health risks related to weight, consider these additional measurements alongside BMI:
Waist Circumference
Measuring your waist circumference helps assess abdominal fat, which is a better predictor of health risks than BMI alone. Excess fat around the waist is associated with higher risk of type 2 diabetes and heart disease.
Increased Health Risk When:
- Men: Waist circumference > 40 inches (102 cm)
- Women: Waist circumference > 35 inches (88 cm)
Body Composition Analysis
Methods such as bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DEXA), and skinfold measurements provide more detailed information about fat, muscle, and bone percentages.
These measurements can be particularly useful for athletes, older adults, and people whose BMI might not accurately reflect their health status.
Track Your Health Beyond BMI
For a more comprehensive understanding of your body composition and health status, consider consulting with a healthcare provider who can recommend appropriate assessments based on your individual needs.
Calculate Your BMI NowHealth Recommendations Based on BMI
While BMI is just one health indicator, it can help guide general recommendations for maintaining or improving your health. Always consult with healthcare professionals for personalized advice.
- Stay physically active with at least 150 minutes of moderate activity weekly
- Eat a balanced diet rich in fruits, vegetables, whole grains, and lean proteins
- Stay hydrated by drinking plenty of water
- Get adequate sleep (7-9 hours for most adults)
- Manage stress through mindfulness, relaxation, or other techniques
- Schedule regular check-ups with healthcare providers
For All BMI Categories
- Consult with healthcare providers to rule out underlying conditions
- Increase caloric intake with nutrient-dense foods
- Include healthy fats like avocados, nuts, and olive oil
- Consider strength training to build muscle mass
- Eat smaller, more frequent meals if you get full quickly
- Track your progress with regular weigh-ins
For Underweight BMI
- Focus on gradual, sustainable weight loss (1-2 pounds per week)
- Reduce portion sizes and be mindful of caloric intake
- Limit processed foods, added sugars, and saturated fats
- Combine cardiovascular exercise with strength training
- Consider working with registered dietitians or weight management specialists
- Monitor other health markers like blood pressure and blood sugar
For Overweight/Obese BMI
Take the First Step Toward Better Health
Understanding your BMI is just the beginning. Use this knowledge as motivation to make positive changes for your long-term health and wellbeing.
Calculate Your BMIConclusion: BMI as Part of Your Health Journey
Body Mass Index serves as a valuable starting point for understanding the relationship between your weight and height, and how it might impact your health. While BMI has limitations, it remains a useful screening tool when used alongside other health assessments.
Remember that health is multifaceted and influenced by numerous factors beyond weight, including genetics, lifestyle, environment, and access to healthcare. A holistic approach to health that considers physical activity, nutrition, mental wellbeing, and regular medical check-ups will always be more valuable than focusing on any single metric.
Whether your BMI falls within the “normal” range or not, the most important step is to work with healthcare professionals to develop a personalized plan that supports your overall health and wellbeing.
Start Your Health Assessment Today
Calculate your BMI, understand what it means, and take informed steps toward your health goals.
Calculate Your BMI NowCalculate Your BMI
BMI Calculator
Calculate your Body Mass Index based on height and weight
Note: This calculator is designed for adults 20 years and older. For children and teens, please use a BMI calculator specifically designed for their age group, as their BMI is interpreted differently.