BMI Calculator — Metric and Imperial Inputs
Calculate adult body mass index from height and weight in metric or imperial units, with the tool’s displayed category.
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How to use it
Choose units, enter weight and height, and calculate your BMI and the displayed adult category.
Good to know
For adults 20+ using the linked CDC guidance. BMI does not measure body fat and is not a diagnosis. Ask a clinician for advice.
See how the formula uses your measurements
Choose metric or imperial units, then enter weight and height. With 70 kg and 175 cm, the calculation is 70 ÷ 1.75², giving BMI 22.9. The tool shows its adult category and a corresponding displayed “healthy weight range” from the same BMI thresholds.
BMI is a screening measure, not a diagnosis
The linked CDC guidance applies adult categories to ages 20 and older. The categories shown use those adult BMI thresholds, but BMI does not directly measure body fat or account for age, sex, pregnancy, muscular build, or health history. It is not appropriate as a diagnosis or treatment decision. For the underlying adult category guidance, see the CDC’s BMI category information; discuss personal health questions with a qualified clinician.
Frequently asked questions
What is a healthy BMI?
CDC adult categories for ages 20 and older label BMI from 18.5 to below 25 as healthy weight. BMI is one screening measure and does not determine individual health.
How is BMI calculated?
BMI is weight in kilograms divided by height in metres squared. Imperial inputs are converted first.
Is BMI accurate for athletes?
Not always. Muscular people can have a high BMI without excess fat.