Health Tool
⚖️ BMI Calculator
Enter your height and weight to see your Body Mass Index, category, healthy weight range, BMI Prime, and Ponderal Index — in metric or imperial units.
📊 BMI Categories (WHO)
Note: These thresholds apply to adults 20 years and older. Children and teens use age- and sex-specific BMI percentiles.
🧠 How BMI is Calculated
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
- The healthy weight range is found by solving the formula backwards for BMI 18.5 and 24.9 at your height.
- BMI Prime = your BMI ÷ 25. Below 1.0 means you are inside the healthy range.
- Ponderal Index = weight (kg) ÷ height (m)³ — a measure that adjusts better for very tall or short people.
Important: BMI is a screening tool, not a medical diagnosis. It does not measure body fat directly and can misclassify muscular athletes, pregnant women, and older adults. Always talk to a healthcare professional about your individual health.
❓ Frequently Asked Questions
What is BMI?
BMI (Body Mass Index) is a simple screening measure calculated from your height and weight. It estimates whether your weight falls in an underweight, normal, overweight, or obese range for your height.
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.
Is BMI accurate for everyone?
No. BMI does not distinguish between muscle and fat, so athletes and very muscular people may be classified as overweight. It is also less reliable for children, pregnant women, and older adults. BMI is a screening tool, not a diagnosis.
What is BMI Prime?
BMI Prime is your BMI divided by 25 (the upper limit of the healthy range). A BMI Prime below 1.0 means you are within the healthy range; above 1.0 means you are above it.
Do I need to use metric or imperial?
Either works — the calculator converts automatically and both formulas produce the same BMI. Switch units at the top and your values convert with you.
Is my data stored anywhere?
No. Everything is calculated in your browser. No height or weight is sent anywhere. No tracking, no ads.
❤️ Support Free Tools
This calculator is free forever. If it helped you, consider buying me a coffee.
☕ Buy Me a Coffee