BMI Calculator - Calculate Your Body Mass Index
Use our free BMI (Body Mass Index) calculator to quickly determine your body mass index based on your height and weight. Body Mass Index is a simple calculation used by healthcare professionals to assess whether you're at a healthy weight for your height.
Our BMI calculator uses both imperial (pounds/inches) and metric (kg/cm) measurements, making it easy for anyone in the United States or worldwide to calculate their BMI instantly. Simply enter your height and weight, and our calculator will provide your BMI score along with a detailed interpretation of what it means for your health.
Whether you're tracking your fitness goals, monitoring your health, or preparing for a medical appointment, this BMI calculator provides accurate results in seconds. The tool also shows you which BMI category you fall into: underweight, normal weight, overweight, or obese.
Your Info:
How to Use This BMI Calculator
- Enter Your Age: Input your age in years (2-120). Age helps provide context for BMI interpretation.
- Select Your Gender: Choose Male or Female. Gender affects body composition and BMI interpretation.
- Choose Height Unit: Select from Feet & Inches, Inches only, Centimeters, or Meters - whatever is most convenient for you.
- Enter Your Height:
- Feet & Inches: Enter separately (e.g., 5 feet 9 inches)
- Inches: Total inches (e.g., 69 inches)
- Centimeters: Height in cm (e.g., 175 cm)
- Meters: Height in meters (e.g., 1.75 m)
- Choose Weight Unit: Select Pounds (lbs) or Kilograms (kg)
- Enter Your Weight: Input your current weight in selected unit
- Click Calculate: Instantly see your BMI result with personalized health information
- Review Your Results: Check your BMI score, category, and personalized recommendations based on your age and gender
🎯 Why Age and Gender Matter in BMI Calculations
Age Considerations: As we age, our body composition naturally changes. Adults over 65 may have slightly higher healthy BMI ranges due to muscle loss (sarcopenia) and changes in bone density. Children and teens require age-specific percentile charts rather than standard adult BMI ranges.
Gender Differences: Women naturally have higher body fat percentages (21-33% for healthy women vs 8-19% for healthy men) due to biological differences. While the BMI formula is the same, interpretation may vary. Women may be healthy at slightly higher BMI values, and men with the same BMI might have more muscle mass.
BMI Standards in the United States
In the United States, the CDC (Centers for Disease Control and Prevention) follows WHO BMI guidelines with some considerations for different populations. American adults should use the standard BMI ranges, while children and teens require age and sex-specific percentile charts.
According to recent CDC data, approximately 42% of American adults are classified as obese (BMI ≥ 30), making BMI monitoring crucial for public health. Regular BMI checks are recommended as part of annual wellness visits covered by most US health insurance plans under the Affordable Care Act.
Understanding Your BMI Results
Your BMI score indicates which weight category you fall into. Here's what each BMI range means for your health according to WHO guidelines:
| BMI Range | Category | Health Status |
|---|---|---|
| Below 18.5 | Underweight | May indicate malnutrition or health issues |
| 18.5 - 24.9 | Normal Weight | Healthy weight range for most adults |
| 25.0 - 29.9 | Overweight | Increased risk of health problems |
| 30.0 - 34.9 | Obese (Class I) | Moderate risk of health complications |
| 35.0 - 39.9 | Obese (Class II) | High risk of serious health issues |
| 40.0 and above | Obese (Class III) | Extremely high risk - medical intervention recommended |
BMI Formula Explained
Understanding the math behind the calculation helps you trust the results:
Imperial Formula (pounds and inches):
BMI = (Weight in pounds ÷ (Height in inches × Height in inches)) × 703
Metric Formula (kilograms and centimeters):
BMI = Weight in kilograms ÷ (Height in meters × Height in meters)
Example Calculation:
For a person who is 5'9" (69 inches) tall and weighs 160 pounds:
BMI = (160 ÷ (69 × 69)) × 703
BMI = (160 ÷ 4,761) × 703
BMI = 0.0336 × 703
BMI = 23.6 (Normal Weight)
Real-World BMI Examples
Example 1: Adult Male
- Height: 5'10" (70 inches)
- Weight: 180 lbs
- BMI: 25.8 (Overweight)
- Recommendation: Minor weight loss of 10-15 lbs would bring BMI to normal range
Example 2: Adult Female
- Height: 5'4" (64 inches)
- Weight: 130 lbs
- BMI: 22.3 (Normal Weight)
- Recommendation: Maintain current healthy weight through balanced diet and exercise
Example 3: Teen (Age 16)
- Height: 5'7" (67 inches)
- Weight: 140 lbs
- BMI: 21.9 (Normal Weight)
- Note: Teen BMI should also consider age and growth patterns. Consult pediatrician for personalized advice.
Limitations of BMI
While BMI is a useful screening tool, it has some limitations:
- Doesn't Account for Muscle Mass: Athletes and bodybuilders may have high BMI due to muscle, not fat
- Doesn't Measure Body Fat Distribution: Two people with same BMI can have different health risks
- Age Differences: BMI standards differ for children, teens, and elderly adults
- Ethnicity Factors: Some ethnic groups have different health risk thresholds
- Pregnancy: BMI calculations don't apply during pregnancy
Alternative Measures: Consider also checking your waist circumference, body fat percentage, and consulting healthcare professionals for complete health assessment.
Frequently Asked Questions (FAQ)
What is a healthy BMI?
A healthy BMI for most adults ranges from 18.5 to 24.9. This range is associated with the lowest risk of weight-related health problems. However, ideal BMI can vary based on age, gender, ethnicity, and muscle mass.
Is BMI accurate for everyone?
BMI is a good general screening tool but isn't perfect for everyone. It may not accurately reflect health for athletes, pregnant women, elderly individuals, or those with high muscle mass. Always consult a healthcare provider for personalized health assessment.
How often should I check my BMI?
For general health monitoring, checking BMI every 3-6 months is sufficient. If you're actively trying to lose or gain weight, monthly checks can help track progress. However, focus on overall health trends rather than daily fluctuations.
Can BMI predict health problems?
BMI is a screening tool that indicates potential health risks. Higher BMI is associated with increased risk of heart disease, diabetes, high blood pressure, and certain cancers. However, BMI alone cannot diagnose health conditions—it's one factor among many.
What's the difference between BMI and body fat percentage?
BMI calculates a ratio of weight to height but doesn't distinguish between muscle and fat. Body fat percentage measures the actual proportion of fat in your body. Someone with high muscle mass might have a high BMI but low body fat percentage.
Does age affect BMI?
Yes, BMI interpretation can vary by age. Children and teenagers use age-specific BMI percentile charts. As adults age, acceptable BMI ranges may shift slightly. Adults over 65 may have slightly higher healthy BMI ranges than younger adults.
How do I lower my BMI?
To lower BMI safely: (1) Create a calorie deficit through balanced diet, (2) Exercise regularly (cardio + strength training), (3) Stay hydrated and get adequate sleep, (4) Track your progress monthly, (5) Consult healthcare providers or nutritionists for personalized plans. Aim for gradual weight loss of 1-2 pounds per week for sustainable results.
Is BMI the same for men and women?
The BMI calculation formula is the same for adult men and women, but interpretation may differ slightly. Women naturally have higher body fat percentages than men. Some health organizations suggest different BMI thresholds based on gender for more accurate health risk assessment.
What BMI is considered obese in the USA?
In the United States, a BMI of 30.0 or higher is classified as obese according to CDC guidelines. Obesity is further divided into Class I (30-34.9), Class II (35-39.9), and Class III (40+). Each class carries increasing health risks.
Can I use BMI calculator for children?
While this calculator works for teens and adults, children under 18 should use age-specific BMI-for-age percentile charts. Pediatric BMI interpretation accounts for age and gender-specific growth patterns. Always consult a pediatrician for children's health assessments.
Health Tips Based on Your BMI
If You're Underweight (BMI < 18.5):
- Consult a doctor to rule out underlying health conditions
- Increase caloric intake with nutrient-dense foods
- Consider strength training to build muscle mass
- Eat more frequently throughout the day
If You're Normal Weight (BMI 18.5-24.9):
- Maintain your current healthy habits
- Continue regular exercise (150 minutes moderate activity per week)
- Eat a balanced diet rich in fruits, vegetables, whole grains
- Monitor your weight periodically
If You're Overweight (BMI 25-29.9):
- Aim for gradual weight loss of 5-10% of body weight
- Reduce portion sizes and limit processed foods
- Increase physical activity to 300 minutes per week
- Track your food intake and calories
If You're Obese (BMI ≥ 30):
- Consult healthcare provider for comprehensive weight management plan
- Consider medical supervision for weight loss
- Focus on sustainable lifestyle changes, not crash diets
- May benefit from nutritionist or weight loss program support
💡 Save Your Results
Bookmark this page to track your BMI over time and monitor your health progress!
📧 Get Weekly Health Tips
Subscribe for BMI tracking reminders and healthy living tips delivered to your inbox!