About this tool
This BMI calculator gives a quick adult body mass index result from height and weight. It supports US units (feet, inches, pounds) and metric units (centimeters, kilograms). The calculation happens entirely in your browser, so your height and weight are not sent anywhere.
BMI is useful because it is simple and standardized. It is also limited. It does not directly measure body fat, muscle mass, waist size, fitness, medication history, or any other health factor. Treat the number as a broad screening metric, not a personal medical conclusion.
How BMI is calculated
For metric inputs, the formula is:
BMI = weight in kilograms / (height in meters x height in meters)
For US inputs, the equivalent formula is:
BMI = 703 x weight in pounds / (height in inches x height in inches)
The result is usually rounded to one decimal place. This calculator uses the standard adult BMI categories: under 18.5, 18.5 to 24.9, 25 to 29.9, and 30 or higher.
What BMI can and cannot tell you
BMI can be useful for population-level screening because it uses only two inputs and the same formula every time. For an individual person, that simplicity is also the weakness. Two people with the same BMI can have very different body composition and health context.
The number can be especially incomplete for athletes, older adults, pregnant people, children, teens, and anyone with a body composition that does not match the average behind the formula. If you are using BMI to make a health decision, use it as one data point and talk with a qualified clinician.
Frequently asked questions
What is BMI?
BMI stands for body mass index. It is a simple ratio of weight to height used as a broad screening number for adults. It does not directly measure body fat, fitness, or health.
What formula does this BMI calculator use?
For metric inputs, BMI equals kilograms divided by meters squared. For US inputs, BMI equals pounds divided by inches squared, multiplied by 703.
Is BMI accurate for everyone?
No. BMI is a rough adult screening metric. It can be misleading for athletes, older adults, pregnant people, children, and anyone whose body composition does not match the population average behind the formula.
Does this calculator store my height or weight?
No. The calculation runs entirely in your browser. Your inputs are not sent to a server, stored, logged, or tracked.
Can children use this BMI calculator?
This calculator uses standard adult BMI categories. Children and teens need age- and sex-specific BMI percentiles, so this tool is not meant for pediatric interpretation.