Check Your Body Mass Index

BMI Calculator

Use this free online calculator to check your BMI (body mass index) based on your height and weight. It also shows your BMI category and a healthy weight range for your height.

Age

Gender

Height

Weight

Note: BMI is a general screening tool for adults. It does not measure body fat directly and may not apply perfectly to athletes, pregnant women, children, or people with higher muscle mass.

Your BMI Result Explained

After you enter your height and weight, the BMI calculator shows your body mass index and places it into a standard adult BMI category.

Your result may fall into one of these ranges:

Underweight: BMI below 18.5
Healthy weight: BMI 18.5 to 24.9
Overweight: BMI 25.0 to 29.9
Obesity: BMI 30.0 or higher

These adult BMI ranges are used by the CDC for adults age 20 and older. BMI can help screen for weight categories, but it should not be used by itself to diagnose health or disease risk.

What Is BMI?

BMI stands for body mass index. It is a number calculated from your height and weight. The purpose of BMI is to give a quick estimate of whether your weight falls within a standard adult weight category. It is widely used because it is simple, fast, and easy to compare across adults.

However, BMI does not directly measure body fat. It also does not show muscle mass, bone density, waist size, fat distribution, or overall health. That is why BMIBox treats BMI as a starting point, not the final answer.

How to Calculate BMI

BMI is calculated by dividing weight by height squared.

For metric units:
BMI = weight in kilograms ÷ height in meters squared

For US units:
BMI = weight in pounds ÷ height in inches squared × 703

For example, if someone weighs 70 kg and is 1.75 m tall.

Their BMI is: 70 ÷ 1.75² = 22.9

A BMI of 22.9 falls within the healthy weight range for most adults.

Adult BMI Categories

Use this quick table to understand your BMI result.

BMI Range	Category	What It Usually Means

Below 18.5

Underweight

Your BMI is below the standard healthy adult range.

18.5 to 24.9

Healthy Weight

Your BMI is within the standard healthy adult range.

25.0 to 29.9

Overweight

Your BMI is above the standard healthy adult range.

30.0 or higher

Obesity

Your BMI falls within the adult obesity range.

For adults, obesity is also divided into three classes:

BMI Range	Obesity Class
30.0 to 34.9	Class 1 Obesity

35.0 to 39.9

Class 2 Obesity

40.0 or higher

Class 3 Obesity

What Is a Healthy BMI Range?

For most adults, a healthy BMI range is 18.5 to 24.9.

A BMI below 18.5 may indicate underweight. A BMI of 25 or higher may indicate excess body weight. A BMI of 30 or higher falls into the obesity range.

But your BMI number should always be understood in context. A muscular person may have a higher BMI without having a high body fat percentage. Someone with a “normal” BMI may still have a higher waist measurement or other risk factors.

When Should You Use This BMI Calculator?

Use this BMI calculator if you want to:

Check your body mass index
Find your adult BMI category
Estimate your healthy weight range
Compare your BMI with a BMI chart
Track changes in your weight over time
Understand whether your weight may be below, within, or above the standard adult range

This calculator is designed for adults. BMI categories are different for children and teens because they are based on age-and-sex percentiles.

FAQs

BMI stands for body mass index. It is a number calculated from height and weight to estimate whether an adult falls into an underweight, healthy weight, overweight, or obesity category.

To calculate BMI using metric units, divide weight in kilograms by height in meters squared. For US units, divide weight in pounds by height in inches squared, then multiply by 703.

For most adults, a normal or healthy BMI is 18.5 to 24.9.

For adults, a BMI from 25.0 to 29.9 is usually considered overweight.

For adults, a BMI of 30.0 or higher is usually considered obesity.

BMI is calculated the same way for adult men and women. However, BMI does not show differences in body fat percentage, muscle mass, or fat distribution.

BMI is useful for quick screening, but it is not a complete health measurement. It does not directly measure body fat, waist size, muscle mass, or health risk.

BMI can place someone in an obesity category, but it should not be used alone as a medical diagnosis. Health professionals may consider waist size, symptoms, lab results, body composition, and medical history.

No. This calculator is designed for adults. Children and teens need BMI-for-age percentiles rather than adult BMI categories.

A high BMI can be a signal to review your overall health, waist size, eating habits, activity level, sleep, and medical history. Speak with a qualified healthcare professional for personal guidance.