BMI Calculator Calculate Body Mass Index

BMI Guide

Free Online BMI Calculator

Our free online BMI calculator helps you calculate Body Mass Index from height and weight. You can use metric units with kilograms and centimeters or US units with pounds, feet and inches.

After calculation, the tool displays your BMI value, a commonly used adult BMI category and an estimated weight range corresponding to BMI values from 18.5 to below 25 for the entered height.

What Is BMI?

BMI stands for Body Mass Index. It is a numerical value calculated from a person's weight relative to height. BMI is commonly used as a screening measure rather than a direct measurement of body fat.

Because the calculation uses only height and weight, people with the same BMI can have different body compositions. Age, muscle mass and other individual factors may affect how a BMI result should be interpreted.

How to Calculate BMI

For metric measurements, divide weight in kilograms by height in meters squared.

For example, a person weighing 70 kilograms with a height of 1.75 meters has a BMI of approximately 22.9.

How to Calculate BMI Using Pounds and Inches

When using pounds and inches, multiply weight in pounds by 703 and divide the result by height in inches squared.

What Is a Healthy BMI Range?

In a commonly used adult BMI classification, values from 18.5 to below 25 are categorized as healthy or normal weight. Values below 18.5 are categorized as underweight, values from 25 to below 30 as overweight and values of 30 or higher within obesity categories.

These categories are screening classifications. A BMI result alone does not provide a complete assessment of individual health.

Understanding Your BMI Result

The calculator compares the calculated BMI with commonly used adult screening thresholds. This provides a quick category label, but the result should be interpreted in context.

For example, a muscular athlete may have a relatively high BMI because muscle contributes to body weight. BMI does not distinguish between weight from muscle, fat, bone or other body tissues.

BMI Calculator for Metric Units

Select the metric option if you know your weight in kilograms and height in centimeters. The calculator automatically converts centimeters to meters before applying the BMI formula.

BMI Calculator for Pounds, Feet and Inches

Select the US unit option to enter weight in pounds and height using feet and inches. The calculator converts the height to total inches and applies the corresponding BMI formula.

Limitations of BMI

BMI has important limitations because it is based only on height and weight. It does not directly measure body fat percentage, fat distribution, muscle mass or overall fitness.

Interpretation can differ for children and teenagers, pregnant people, older adults, athletes and people with high muscularity. Age-specific or clinically appropriate assessment methods may be needed.

BMI vs Body Fat Percentage

BMI and body fat percentage are different measures. BMI is calculated from height and weight, while body fat percentage estimates how much of total body weight consists of fat tissue.

Two people with the same height and weight will have the same BMI even if their proportions of muscle and body fat are different.