BMI Calculator
Calculate your Body Mass Index instantly. Metric or imperial units – all processing stays in your browser.
What is BMI and how is it calculated?
Body Mass Index (BMI) is a simple measure that uses your height and weight to estimate body fat. It is widely used as a screening tool to categorize underweight, healthy weight, overweight, and obesity.
The formula is:
- Metric: BMI = weight (kg) / (height (m))²
- Imperial: BMI = (weight in lbs × 703) / (height in inches)²
For example, a person who is 170 cm tall and weighs 70 kg has a BMI of 70 / (1.7)² = 24.2.
Understanding BMI categories
- Underweight: Below 18.5
- Normal weight: 18.5 – 24.9
- Overweight: 25 – 29.9
- Obese: 30 and above
These categories are based on World Health Organization guidelines. Use our Unit Converter if you need to convert between metric and imperial measurements.
Limitations of BMI
BMI is a useful screening tool but does not directly measure body fat. Athletes with high muscle mass may have a high BMI without excess fat. Similarly, older adults may have normal BMI but low muscle mass. Always consult a healthcare professional for a complete assessment.
Why use Pencilfree BMI Calculator?
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Frequently Asked Questions
How is BMI calculated?
BMI = weight (kg) / (height (m))². For imperial: (weight in lbs × 703) / (height in inches)².
What do the BMI categories mean?
Underweight: <18.5, Normal: 18.5–24.9, Overweight: 25–29.9, Obese: 30 or higher.
Is BMI accurate for everyone?
BMI is a general indicator, but it may not account for muscle mass, age, or other factors. Consult a health professional for personalized advice.
Do you store my data?
No. All calculations happen in your browser. We never see or store any personal data.