A BMI calculator estimates body mass index from height and weight. Adults often use BMI as one general screening measure, but it does not directly measure body fat or tell the whole story about a person’s health. Age, muscle mass, pregnancy, and other factors can affect how a BMI result should be understood.
How BMI is calculated
In the metric system, BMI is weight in kilograms divided by height in meters squared. In US customary units, the calculation uses weight in pounds and height in inches, with a conversion factor of 703. A calculator can handle the arithmetic once you enter the correct measurements.
Understand the result in context
For adults, BMI ranges are commonly used as screening categories, not as a diagnosis. The same number can mean different things for different people, and BMI is interpreted differently for children and teens. If you have concerns about weight or health, discuss the result with a qualified healthcare professional rather than making decisions based on one number alone.
Related tools paragraph: A body mass index tool can calculate BMI and help you compare a result with a BMI chart. Use health calculators for related estimates, explore free online calculators, or visit All calculators for other tools.
Frequently Asked Questions
How do I calculate BMI?
Enter your height and weight; the calculator applies the BMI formula.
What is a normal adult BMI range?
A commonly used adult screening range is 18.5 to 24.9, but it does not diagnose health.
Does BMI measure body fat directly?
No. BMI uses height and weight and does not directly measure body fat.
Is BMI calculated differently for children?
Yes. Children and teens are assessed using age- and sex-specific percentiles.
Should I make health decisions based only on BMI?
No. Consider it one screening measure and discuss concerns with a healthcare professional.
