BMI Calculator help

BMI Calculator Manual

This free calculation is for adults age 20 or older and reports the corresponding CDC adult BMI screening category, not a medical diagnosis.

Confirm the adult age range

Choose Yes only if the person is 20 or older. The page does not ask for a birthdate or sex. For children and teens ages 2–19, use the CDC Child and Teen BMI Calculator. This app does not cover children under 2.

Enter U.S. or metric measurements

The default mode uses pounds, whole feet, and inches from zero to less than twelve. Metric mode uses kilograms and centimeters. Inputs accept whole numbers or decimals with up to three places (feet must be a whole number). Height and weight must be greater than zero; supported engineering limits are 300 cm and 1,000 kg after conversion. These limits do not define a clinically normal body size.

Read the result

The calculator shows BMI to one decimal place and assigns a CDC adult BMI category using the unrounded value: less than 18.5 is Underweight; 18.5 to less than 25 is Healthy weight; 25 to less than 30 is Overweight; and 30 or greater is Obesity. The same adult categories apply regardless of sex.

Rounding near boundaries

For example, 99.9 kg at 200 cm yields an unrounded BMI of 24.975, displayed as 25.0. Its correct adult category remains Healthy weight. A note explains any apparent mismatch. Tiny positive BMI values are not presented as unqualified zero.

Recalculate, try an example and reset

Editing a value clears the prior result; Copy, CSV and Print are disabled until recalculation. Try example supplies illustrative measurements, not recommended goals. Reset also clears the age confirmation. Switching units with active measurements requires confirmation and clears those measurements; it never treats pounds as kilograms.

Copy, CSV and Print / Save PDF

Exports only use the current result and include inputs, units, screening category, limitations, and a reference to the CDC. Copy puts this information on your clipboard. CSV downloads a local file. Print / Save PDF uses your browser’s print dialog. These actions can store or expose personal measurement values on your own device, so review them before sharing.

Medical and privacy limitations

BMI is a screening measurement, not a diagnosis, a measurement of body fat, treatment advice or a substitute for professional evaluation. The app does not ask for sensitive clinical history, store calculation history, or send measurement values to Mycelgrid for processing. Platform-level browser/technical data handling is described by Mycelgrid Privacy Policy and Terms.

Government sources

CDC adult categories · CDC about BMI · NIST units. Mycelgrid is not affiliated with or endorsed by these agencies.