BMI Calculator
Calculate your Body Mass Index and understand your health metrics.
BMI Calculator — Complete User Guide
The Body Mass Index (BMI) is a widely used screening tool that helps assess whether a person has a healthy body weight relative to their height. It is calculated by dividing a person's weight in kilograms by the square of their height in meters. While BMI does not directly measure body fat, it correlates well with more direct measures and is used by healthcare professionals worldwide as a quick, inexpensive indicator of weight status.
The World Health Organization (WHO) defines standard BMI categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25.0–29.9), and obese (30.0 and above). These thresholds apply to most adults aged 20 and older, regardless of sex or body frame. Athletes and muscular individuals may have a higher BMI without excess body fat, so BMI should always be interpreted alongside other health indicators such as waist circumference, body fat percentage, and overall fitness level.
Using this calculator is simple: enter your height and weight, select your preferred unit system, and click Calculate. The result displays your BMI value along with the corresponding WHO category and a color-coded indicator for quick visual reference. For best accuracy, measure your height without shoes and your weight without heavy clothing. Re-check your BMI periodically, especially after significant weight changes, pregnancy, or changes in activity level.
Understanding your BMI helps you make informed decisions about diet, exercise, and medical consultations. If your BMI falls outside the normal range, consider discussing it with a healthcare provider who can evaluate your individual health profile and recommend personalized strategies. This tool is for informational purposes only and does not constitute medical advice.
Frequently Asked Questions
What is a healthy BMI range?
A healthy BMI for most adults is between 18.5 and 24.9, according to the World Health Organization. Some guidelines use slightly different cutoffs for specific populations.
Is BMI accurate for everyone?
BMI is a screening tool, not a diagnostic one. It may overestimate body fat in athletes and underestimate it in older adults or those with muscle loss. Always consider it alongside other health metrics.
Can children use this BMI calculator?
No. BMI interpretation for children and teens uses age- and sex-specific percentiles rather than fixed adult thresholds. Consult a pediatrician for child weight assessment.
How often should I check my BMI?
Checking your BMI every few months or after significant lifestyle changes is reasonable. Daily fluctuations are normal; focus on trends over time rather than single readings.