This BMI calculator helps fitness enthusiasts, athletes, and health-conscious individuals track their body mass index. It supports both metric and imperial units to fit your preferred measurement system. Use it to monitor progress toward your fitness or nutrition goals.
BMI Calculator
Calculate your body mass index and get a detailed health breakdown
Your BMI Results
How to Use This Tool
Start by selecting your preferred unit system (metric or imperial) from the dropdown menu.
Enter your current weight in the corresponding field (kilograms for metric, pounds for imperial).
Enter your height: for metric, input centimeters; for imperial, input feet and inches.
Click the Calculate BMI button to generate your results.
Use the Reset button to clear all inputs and start over.
Click Copy Results to save your BMI breakdown to your clipboard.
Formula and Logic
BMI is calculated using two standard formulas depending on your unit system:
- Metric: BMI = weight (kg) / (height (m))². To convert height from centimeters to meters, divide by 100.
- Imperial: BMI = (weight (lbs) / (height (inches))²) * 703. To convert height to inches, multiply feet by 12 and add inches.
The resulting BMI value is classified into four categories:
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5–24.9
- Overweight: BMI 25–29.9
- Obese: BMI ≥ 30
Healthy weight ranges are derived by reversing the BMI formula using the normal weight category bounds (18.5 and 24.9) for your height.
Practical Notes
BMI is a general screening tool and does not account for individual factors like muscle mass, bone density, or body composition. Athletes with high muscle mass may have a higher BMI without excess body fat.
This tool is not a substitute for professional medical advice. Always consult a doctor or registered dietitian before making significant changes to your diet or exercise routine.
BMI categories may vary slightly for certain populations, including children, pregnant people, and older adults. This calculator uses standard adult classifications for ages 18–65.
Track your BMI over time rather than relying on a single measurement to monitor fitness or nutrition progress.
Why This Tool Is Useful
Quickly assess your body mass index without manual calculations or unit conversions.
Supports both metric and imperial units to fit your regional or personal measurement preferences.
Provides a detailed breakdown including BMI value, category, healthy weight range, and status relative to normal weight.
Copy results to your clipboard to share with trainers, dietitians, or healthcare providers.
Reset functionality lets you test multiple scenarios (e.g., projected weight loss) quickly.
Frequently Asked Questions
Is BMI accurate for athletes?
No, BMI does not distinguish between muscle and fat. Athletes with high muscle mass often have elevated BMI values that do not reflect excess body fat. Use additional metrics like body fat percentage for a more complete assessment.
Can I use this calculator if I'm pregnant?
This calculator uses standard adult BMI classifications, which do not apply to pregnant or breastfeeding people. Consult your obstetrician for appropriate weight gain guidelines during pregnancy.
How often should I check my BMI?
For most adults, checking BMI every 4–8 weeks is sufficient to track long-term trends. More frequent checks may lead to unnecessary concern over minor fluctuations from water weight or digestion.
Additional Guidance
Pair BMI tracking with other health metrics like waist circumference, blood pressure, and resting heart rate for a fuller picture of your physical health.
If your BMI falls outside the normal range, consult a healthcare provider to rule out underlying conditions before starting a new diet or exercise program.
Use this tool to set realistic weight goals: calculate the weight corresponding to a BMI of 22 (the midpoint of the normal range) to set a sustainable target.