Free BMI Calculator
Calculate your Body Mass Index (BMI) instantly and check if your weight is in the healthy range.
BMI Calculator
How BMI is Calculated
Metric Formula:
BMI = weight (kg) / (height (m))²
Imperial Formula:
BMI = (weight (lbs) × 703) / (height (inches))²
How to Use This BMI Calculator
Step 1: Choose Your Unit System
Select your preferred unit system:
- Metric: Use if you know your height in centimeters and weight in kilograms
- Imperial: Use if you know your height in feet/inches and weight in pounds
Step 2: Enter Your Measurements
For accurate results:
- Height: Enter your height precisely
- Metric: Enter in centimeters (e.g., 175)
- Imperial: Enter feet and inches separately
- Weight: Enter your current weight
- Metric: Enter in kilograms (e.g., 70)
- Imperial: Enter in pounds (e.g., 154)
Step 3: Calculate and Interpret Results
After clicking 'Calculate BMI', you'll receive:
- Your precise BMI number
- Your weight category classification
- Health implications for your BMI range
- Recommendations based on your results
Step 4: Regular Monitoring
For effective weight management:
- Calculate your BMI regularly (every 1-2 months)
- Track changes over time
- Use the same unit system for consistent results
- Consider other health metrics alongside BMI
Pro Tips for Accurate Results
- Measure your height in the morning (we're slightly taller)
- Weigh yourself at the same time of day
- Use consistent measuring tools
- Remove shoes and heavy clothing for measurements
Note: BMI is a reliable screening tool used by health professionals worldwide to assess healthy weight ranges. However, it should be used as part of a broader health assessment.
BMI Categories and Ranges
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 16.0 | Severe Underweight | Severe health risks |
| 16.0 - 16.9 | Moderate Underweight | Moderate health risks |
| 17.0 - 18.4 | Mild Underweight | Mild health risks |
| 18.5 - 24.9 | Normal Weight | Lowest health risks |
| 25.0 - 29.9 | Overweight | Increased health risks |
| 30.0 - 34.9 | Class I Obesity | High health risks |
| 35.0 - 39.9 | Class II Obesity | Very high health risks |
| 40.0 and above | Class III Obesity | Extremely high health risks |
Health Implications of BMI
Underweight (BMI below 18.5)
- Weakened immune system
- Nutrient deficiencies
- Osteoporosis risk
- Fertility issues
- Delayed wound healing
Normal Weight (BMI 18.5-24.9)
- Lower risk of heart disease
- Better blood sugar control
- Reduced joint problems
- Better fertility
- Improved energy levels
Overweight (BMI 25-29.9)
- Increased risk of type 2 diabetes
- Higher blood pressure
- Joint stress
- Sleep apnea risk
- Cardiovascular concerns
Obesity (BMI 30 or greater)
- High risk of heart disease
- Type 2 diabetes
- Certain cancers
- Breathing problems
- Mental health impacts
Frequently Asked Questions
What is BMI and why is it important?
Body Mass Index (BMI) is a numerical value calculated from your weight and height. It's a widely used screening tool that can indicate whether you're at a healthy weight for your height. BMI is important because it can help identify potential weight-related health risks and guide healthcare decisions.
How accurate is BMI as a health indicator?
While BMI is a useful screening tool, it has limitations. It doesn't directly measure body fat or overall health status. Athletes with high muscle mass might have a high BMI but not be overweight. Similarly, elderly individuals might have a normal BMI but have low muscle mass. It's best used alongside other health assessments.
How often should I check my BMI?
It's recommended to check your BMI every 6-12 months as part of your regular health monitoring. However, if you're actively working on weight management, you might want to check it more frequently. Remember to discuss significant BMI changes with your healthcare provider.
What should I do if my BMI is outside the healthy range?
If your BMI falls outside the healthy range (18.5-24.9), consider:
- Consulting with a healthcare provider
- Evaluating your diet and exercise habits
- Setting realistic weight management goals
- Getting support from a registered dietitian
- Regular health monitoring
Are there different BMI calculations for children and teens?
Yes, BMI for children and teens (aged 2-19) is calculated using the same formula but interpreted differently. It's compared to typical values for other children of the same age and sex, using percentiles. This is because body composition varies significantly with age and between boys and girls during development.
Related Health Calculators
Calorie Calculator
Calculate your daily calorie needs based on your BMI, age, activity level, and weight goals.
Macro Calculator
Determine your ideal macronutrient ratios for optimal nutrition based on your BMI and fitness goals.
Body Fat Calculator
Get a more detailed body composition analysis to complement your BMI measurement.
References
- World Health Organization. (2024). Body mass index - BMI. Retrieved from WHO website
- Centers for Disease Control and Prevention. (2024). About Adult BMI. Retrieved from CDC website
- National Health Service. (2024). What is the body mass index (BMI)? Retrieved from NHS website
- National Institute of Health. (2024). Classification of Overweight and Obesity by BMI. Retrieved from NIH website