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Adult BMI Calculator – Metric & US Units
Calculate your adult Body Mass Index from your height and weight, view the corresponding CDC adult BMI category, and understand the result's limitations.
This calculator uses your height and weight to calculate Body Mass Index and identify the corresponding adult BMI category. It supports metric and US units and is intended only for adults age 20 or older.
What Is BMI?
Body Mass Index, or BMI, is a person's weight in kilograms divided by the square of their height in meters. It is a quick screening measure used to evaluate weight relative to height, but it is not a direct measurement of body fat or overall health.
Adult BMI Categories
The categories used by this calculator follow the current adult ranges published by the U.S. Centers for Disease Control and Prevention: below 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25.0 to 29.9 is overweight, and 30.0 or higher is obesity. Obesity is further divided into Classes 1, 2, and 3.
What Does BMI Not Measure?
BMI does not distinguish between fat, muscle, and bone mass, and it does not show where body fat is carried. Two people with the same BMI can have different body compositions and health considerations.
How Should an Adult BMI Result Be Used?
BMI is one potential health indicator rather than a diagnosis. A more complete assessment may also consider medical history, health behaviors, blood pressure, physical findings, muscle mass, glucose, cholesterol, and other relevant information.
How to Use the Adult BMI Calculator
Select metric or US units, enter your age, height, and weight, and choose Calculate BMI. The age field confirms that the adult categories are appropriate; age does not otherwise change the adult BMI formula.
Private Browser-Based Calculation
Your age, height, and weight are processed only in your browser. ORVITech does not upload these measurements to a server, store them in an account, or add them to a calculation history.
How Is the Result Calculated?
Metric: BMI = Weight in kilograms ÷ Height in meters² US units: BMI = (Weight in pounds ÷ Height in inches²) × 703
Adult BMI Calculation Example
An adult who weighs 70 kg and is 1.75 meters tall has a BMI of 70 ÷ 1.75². Because 1.75² equals 3.0625, the result is approximately 22.9 kg/m², which falls within the adult healthy weight category.
Frequently Asked Questions
What is considered a healthy BMI for an adult?
For adults age 20 or older, a BMI from 18.5 to 24.9 falls within the healthy weight category. The category is a screening classification and does not by itself establish that a person is healthy.
Where do these adult BMI categories come from?
The ranges used by this calculator follow the adult BMI categories published by the U.S. Centers for Disease Control and Prevention.
Does age change the adult BMI formula?
No. For adults age 20 or older, the formula and standard categories do not change based on age. The age field prevents the adult interpretation from being applied to children and teenagers.
Is BMI an exact measurement of body fat?
No. BMI is calculated from height and weight. It does not directly measure body fat or distinguish among fat, muscle, and bone mass.
Can BMI determine whether I am healthy?
No. BMI is one screening measure and is not a diagnosis. Health assessment may also involve medical history, behaviors, physical examination, blood pressure, laboratory results, and other individual factors.
Should children and teenagers use this calculator?
No. For people ages 2 through 19, BMI is interpreted using age- and sex-specific percentiles. They need a calculator designed for children and teenagers.
Are my measurements uploaded or stored?
No. This calculation runs locally in your browser, and ORVITech does not upload or store your age, height, or weight.
Is this calculator a substitute for medical advice?
No. The result is informational and should not replace advice, diagnosis, or treatment from a qualified healthcare professional.