BMI Calculator

Use this free BMI calculator to calculate body mass index with metric or imperial units and see adult BMI categories. Calculate body mass index from height and weight with metric or imperial units and adult BMI categories.

Privacy note: For normal use, the interactive workflow is designed to run in your browser and keep the task fast without account friction.

How to use this tool

  1. Choose metric or imperial units: Use centimeters and kilograms or feet, inches, and pounds.
  2. Enter height and weight: Add accurate measurements to calculate body mass index.
  3. Review the BMI result: Check the BMI number, adult BMI category, formula, and educational context. Use the result as a screening estimate, not medical advice.

About this tool

Use this free BMI calculator to calculate body mass index from height and weight using metric or imperial units. This page targets high-intent health calculator searches such as BMI calculator, body mass index calculator, free BMI calculator, adult BMI calculator, BMI calculator metric, BMI calculator imperial, BMI chart, healthy BMI calculator, BMI formula, and weight category calculator. BMI is calculated from weight relative to height and is commonly used as an adult screening measure. For adults age 20 and older, common BMI categories are underweight below 18.5, healthy weight from 18.5 to less than 25, overweight from 25 to less than 30, and obesity at 30 or greater. BMI is not a diagnosis and does not directly measure body fat, muscle mass, waist size, body fat distribution, pregnancy status, or personal medical history. Children and teens need BMI-for-age percentiles based on age and sex.

FAQ

What is a BMI calculator?

A BMI calculator is an online tool that calculates body mass index from height and weight. BMI is commonly used as an adult screening measure for weight categories, but it does not directly measure body fat or diagnose health.

How do I calculate BMI?

For metric units, BMI equals weight in kilograms divided by height in meters squared. For US customary units, BMI equals weight in pounds divided by height in inches squared, multiplied by 703.

What are the adult BMI categories?

For adults age 20 and older, common BMI categories are underweight below 18.5, healthy weight from 18.5 to less than 25, overweight from 25 to less than 30, and obesity at 30 or greater.

Is BMI accurate for everyone?

BMI is useful for quick screening, but it has limits. It does not distinguish muscle from fat, does not show body fat distribution, and may be less informative for athletes, older adults, pregnant people, and some medical situations.

Can children use this BMI calculator?

This page is designed for adult BMI screening. Children and teens need BMI-for-age percentiles based on age and sex, so their results should be interpreted with a pediatric growth chart or a qualified healthcare professional.

Does BMI diagnose obesity or health risk?

No. BMI is a screening measure, not a diagnosis. A healthcare professional may consider BMI along with waist circumference, medical history, blood pressure, labs, body composition, symptoms, medications, and other factors.

What is a healthy BMI?

For most adults, the standard healthy weight BMI category is 18.5 to less than 25. Your personal health picture can still depend on body composition, waist measurement, fitness, age, medical conditions, and clinical guidance.