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Free BMI Calculator Online – Body Mass Index Calculator

Calculate your Body Mass Index (BMI) to understand your weight category and assess health risks. Our BMI calculator supports both metric (kg/cm) and imperial (lbs/ft/in) units, providing instant results based on WHO standards.

Calculate Your BMI

Your BMI

Normal weight

BMI Formula

Body Mass Index (BMI) is calculated using a simple formula that relates your weight to your height:

Metric Units:

BMI = weight (kg) / [height (m)]²

Imperial Units:

BMI = 703 × weight (lbs) / [height (in)]²

The result is a single number that falls into one of several categories defined by the World Health Organization (WHO).

How to Use the BMI Calculator

Select Height Unit: Choose between centimeters, feet, or inches
Enter Your Height: Input your height in the selected unit
Select Weight Unit: Choose between kilograms or pounds
Enter Your Weight: Input your current weight in the selected unit
View Results: Your BMI and weight category appear instantly
Interpret Results: Check the category to understand your weight status

BMI Categories (WHO Standards)

Underweight: BMI less than 18.5 - May indicate malnutrition or health issues
Normal weight: BMI 18.5 to 24.9 - Considered healthy weight range
Overweight: BMI 25 to 29.9 - Increased health risk, lifestyle changes recommended
Obese: BMI 30 or greater - Significant health risks, medical attention advised

Example Calculation

Example: A person who is 170 cm tall and weighs 70 kg

Calculation:

Height in meters = 170 cm ÷ 100 = 1.7 m
Height squared = 1.7 × 1.7 = 2.89 m²
BMI = 70 kg ÷ 2.89 m² = 24.2

Result: BMI of 24.2 falls in the "Normal weight" category

Understanding Your BMI Results

What BMI Measures

BMI is a screening tool that estimates body fat based on height and weight. It's widely used because it's simple, quick, and doesn't require special equipment. However, BMI has limitations:

Doesn't measure body fat directly: BMI can't distinguish between muscle and fat
Doesn't consider body composition: Athletes may have high BMI due to muscle mass
Age and gender variations: Healthy BMI ranges may vary by age and gender
Ethnicity differences: Some ethnic groups have different health risk thresholds

When to Consult a Doctor

Consider consulting a healthcare professional if:

Your BMI is outside the normal range (18.5-24.9)
You have sudden or unexplained weight changes
You have concerns about your weight or health
You're planning significant lifestyle changes
You have existing health conditions affected by weight

Frequently Asked Questions

Q: Is BMI accurate for everyone?

A: BMI is a useful screening tool for most adults, but it has limitations. It may not be accurate for athletes, bodybuilders, pregnant women, elderly people, or children. It doesn't account for muscle mass, bone density, or body composition. For a complete health assessment, consult a healthcare professional.

Q: What is a healthy BMI?

A: According to WHO standards, a healthy BMI for adults is between 18.5 and 24.9. However, what's healthy can vary based on age, ethnicity, muscle mass, and overall health. Always consider BMI as one indicator among many, not the sole measure of health.

Q: Can BMI be used for children?

A: Children and teenagers require different BMI calculations that account for age and gender. Pediatric BMI uses percentile charts rather than fixed categories. Consult a pediatrician for accurate assessment of children's weight status.

Q: How often should I check my BMI?

A: Checking BMI monthly or quarterly is sufficient for most people tracking weight management goals. More frequent checks aren't usually necessary unless advised by a healthcare provider. Focus on long-term trends rather than daily fluctuations.

⚠️ Health Disclaimer

This BMI calculator is for informational and educational purposes only. It does not provide medical diagnosis or replace professional medical advice. BMI is a screening tool with limitations and should not be the sole factor in health decisions. Always consult qualified healthcare professionals for medical concerns, health conditions, personalized advice, or before starting any diet or exercise program.