BMI Calculator

Understanding BMI (Body Mass Index)

Body Mass Index is a screening measure that compares weight to height. The CDC notes that BMI is a quick, low-cost way to estimate weight categories in adults, but it is not a diagnostic tool and should be considered alongside other health factors.

How BMI is calculated

BMI is calculated using the formula: BMI = weight (kg) / height (m)². This calculator accepts metric inputs or converts imperial units to metric before calculating the result.

Adult BMI categories

• Underweight: below 18.5
• Healthy weight: 18.5 to 24.9
• Overweight: 25.0 to 29.9
• Obesity: 30.0 and above

These ranges are commonly used by public health organizations such as the WHO for adults aged 20 and older.

Important limitations

• BMI does not directly measure body fat or distinguish between muscle and fat.
• It can be less accurate for athletes, older adults, or people with different body compositions.
• BMI categories for children and teens use age- and sex-specific percentiles, not adult ranges.

Next steps

Use BMI as a starting point. If you are concerned about your result, consider speaking with a healthcare professional who can look at additional measures like waist circumference, blood pressure, and cholesterol.

Sources

• CDC: About Body Mass Index (BMI)
• CDC: BMI for children and teens
• WHO: Obesity and overweight (BMI classification)