BMI Calculator

Body Mass Index (BMI) is weight in kilograms divided by height in metres squared. It is a screening measure, not a direct measure of body fat or a diagnosis.

Divide weight in kilograms by height in metres squared. For US measurements, the familiar formula is weight in pounds divided by height in inches squared, multiplied by approximately 703. This calculator converts units precisely before calculating.

The standard adult category named Healthy Weight covers BMI 18.5 to less than 25. A category does not establish that an individual is healthy; other health information matters.

For adults 20 and older: below 18.5 is Underweight; 18.5 to less than 25 is Healthy Weight; 25 to less than 30 is Overweight; and 30 or above is the Obesity category. The latter is divided into Classes 1, 2 and 3 at 30, 35 and 40.

The standard adult BMI formula and category thresholds do not depend on sex. Body composition and other factors may still differ, which is one reason BMI needs context.

Adults use standard category thresholds from age 20. Ages 2–19 require BMI-for-age assessment using age- and sex-specific growth references. Older adults may also need additional individual context.

BMI calculates weight relative to height accurately, but cannot distinguish muscle from fat. People with high muscle mass may have a higher BMI without having high body fat.

No. BMI uses height and weight. Body-fat assessment uses different methods and provides different information. BMI and body-fat percentage are not interchangeable.

There is no single adult-style BMI range for all children. Interpretation depends on age and sex using a validated growth reference and should consider growth over time.

The basic BMI formula is the same, but interpretation uses age- and sex-specific percentiles. EvryNest does not yet provide validated child percentiles; the Child / Teen tab links to the CDC calculator instead.

Some clinical guidance, including NICE, uses lower practical thresholds for certain ethnic populations because cardiometabolic risk may occur at lower BMI. EvryNest shows standard adult categories and never infers or changes thresholds based on location or ethnicity.

Standard current-weight BMI is not interpreted in the same way during pregnancy. Pre-pregnancy BMI is used in pregnancy-related guidance. This tool does not provide pregnancy weight recommendations.

BMI may need additional context at age 65 and older. Health conditions, muscle mass, functional status and other factors can affect how a healthcare professional interprets it.

This page calculates the weight corresponding to BMI 18.5–24.9 at the entered height. It is a mathematical reference interval, not a personalized recommendation or a target weight.

Yes. Select US Units and enter whole feet, inches from 0 to less than 12, and pounds. Switching units preserves the underlying measurements without rounding the calculation.

This calculator does not save measurements, use a backend for calculation, or place health values in URLs or analytics events. Results remain in this page until it is closed or reset. Share copies only the BMI summary after you explicitly select Share.