What is the BMI Calculator?
The Body Mass Index (BMI) Calculator is a standardized health screening tool. It evaluates a person's weight in relation to their height to categorize them as underweight, healthy weight, overweight, or obese, helping to identify potential health risks.
How to Calculate Body Mass Index (Formulas)
The BMI formula uses straightforward anthropometric measurements. (Our calculator automatically supports both metric and imperial inputs).
- Metric Formula: BMI = Weight (kg) / [Height (meters)]^2
- Imperial/US Formula: BMI = 703 * (Weight (lbs) / [Height (inches)]^2)
Formula Sources, Review Notes & Disclaimer
Formula source: CDC adult BMI formula and category ranges. Source.
Last updated: June 19, 2026. Reviewed: June 19, 2026 for formula accuracy, source alignment, and plain-language limitations.
Disclaimer: This BMI result is a screening estimate only and is not a diagnosis. Athletes, pregnant people, older adults, and anyone with health concerns should discuss results with a qualified clinician.
Frequently Asked Questions
What are the standard BMI weight categories?
According to the World Health Organization (WHO): Underweight is below 18.5, Healthy Weight is 18.5 to 24.9, Overweight is 25.0 to 29.9, and Obesity is 30.0 or higher.
Is BMI an accurate measure of body fat?
BMI is a mathematical estimate and does not directly measure body fat percentage. Because muscle tissue is significantly denser than fat, muscular athletes and bodybuilders are frequently categorized as "overweight" or "obese" despite having very low body fat.
Why is BMI still used by doctors?
Despite its flaws on an individual level, BMI remains the most cost-effective, non-invasive, and rapid screening tool for tracking obesity trends across large populations and identifying patients who may need further metabolic testing.