About the BMI Calculator

The Body Mass Index (BMI) Calculator helps you quickly determine your BMI and weight status based on your height, weight, and age. You can use the Metric or Imperial units tabs to enter your measurements. This tool also computes the Ponderal Index and provides detailed explanations of your results.

What is BMI?

BMI is a widely used indicator of body fatness, calculated from your height and weight. It helps categorize individuals as underweight, normal weight, overweight, or obese. While BMI is a useful screening tool, it does not directly measure body fat or account for factors like age, sex, ethnicity, or muscle mass.

How to Use This Calculator

• Enter your age, height, and weight in the appropriate fields.
• Switch between Metric (cm/kg) and Imperial (ft/in/lbs) units as needed.
• Your BMI, category, and healthy weight range will be displayed instantly.
• The calculator also provides a Ponderal Index for additional insight.

BMI Categories for Adults (WHO)

BMI for Children and Teens (CDC)

For individuals aged 2–20, BMI is interpreted using percentiles:

• Underweight: < 5th percentile
• Healthy weight: 5th–85th percentile
• At risk of overweight: 85th–95th percentile
• Overweight: > 95th percentile

Health Risks of Abnormal BMI

• Overweight/Obesity: Increases risk of heart disease, diabetes, high blood pressure, stroke, certain cancers, sleep apnea, and more.
• Underweight: Raises risk of malnutrition, osteoporosis, immune deficiencies, fertility issues, and complications from surgery.

Limitations of BMI

• BMI does not distinguish between muscle and fat mass.
• May misclassify muscular individuals as overweight or obese.
• Does not account for age, sex, ethnicity, or body composition.
• Should be considered alongside other health assessments.

BMI Formula

• Metric: BMI = weight (kg) / [height (m)]²
• Imperial: BMI = 703 × weight (lbs) / [height (in)]²

BMI Prime

BMI Prime is your BMI divided by the upper limit of the normal BMI range (25 kg/m²). A value above 1 indicates overweight, while below 1 is normal or underweight.

• BMI Prime = BMI / 25

Ponderal Index

The Ponderal Index (PI) is similar to BMI but uses height cubed instead of squared. It is more reliable for very tall or short individuals.

• Metric: PI = weight (kg) / [height (m)]³
• Imperial: PI = height (in) / ∛weight (lbs)

Summary

BMI is a useful screening tool for assessing healthy body weight, but it is not a diagnostic measure. Always consult a healthcare provider for a comprehensive health assessment.