What Is a BMI Calculator?

A BMI Calculator uses a person’s weight and height to calculate Body Mass Index. BMI is commonly used as a simple screening measure for adult weight categories.

This FreeToolsPoint BMI Calculator supports both metric and imperial measurements. Metric users can enter kilograms and centimeters. Imperial users can enter pounds together with feet and inches.

The calculator displays the calculated number to one decimal place and compares it with adult BMI category ranges. It does not ask for a name, email address, age, account or registration.

• Calculates BMI using metric measurements.
• Calculates BMI using imperial measurements.
• Displays an adult screening category.
• Runs through JavaScript in the browser.
• Works on mobile phones, tablets and desktop computers.

BMI Calculator Formula

Body Mass Index is calculated by comparing weight with the square of height. The formula depends on whether metric or imperial measurements are used.

Metric BMI Example

An adult who weighs 70 kilograms and is 1.75 meters tall would have a calculated BMI of approximately 22.9:

Based on the adult ranges displayed above, that result would fall within the healthy weight screening category. The category alone does not determine the person’s overall health.

How to Use the BMI Calculator

1. Select Metric when using kilograms and centimeters, or Imperial when using pounds, feet and inches.
2. Enter your current weight in the required unit.
3. Enter your height carefully and check the selected unit.
4. Select the Calculate BMI button.
5. Review your calculated BMI number and adult screening category.
6. Consider the result together with other relevant health information rather than using BMI alone.

Tips for Entering Measurements

• Confirm that kilograms are not entered in the pounds field.
• Enter centimeters rather than meters in the metric height field.
• Enter only the additional inches from zero to less than twelve.
• The inches field may be left blank when the height is an exact number of feet.
• Use recent and reasonably accurate measurements.

Understanding Your BMI Calculator Result

The BMI number places an adult within a general screening category. It does not identify the cause of a person’s weight, directly measure body fat or determine whether a person has a medical condition.

Two people with the same BMI may have different body composition, medical history, physical activity, muscle mass and other health factors. A healthcare professional may consider BMI together with additional information.

A result outside the healthy weight screening range does not automatically establish that a person is unhealthy. Similarly, a result within that range does not guarantee good health.

Important Limitations of BMI

BMI is calculated from height and weight. It does not directly measure body fat, muscle mass, bone density or the distribution of body fat.

The same BMI can therefore have a different meaning for different people. BMI should be viewed as one possible health indicator rather than a complete individual assessment.

• It cannot distinguish muscle from body fat.
• It does not show where body fat is distributed.
• It does not include medical history or laboratory findings.
• Adult categories are not appropriate for children and teenagers.
• Pregnancy and other individual circumstances require appropriate professional assessment.

A healthcare professional may consider other information such as medical history, physical examination, health behaviours, laboratory findings or additional body measurements.

BMI Calculator Privacy

The height and weight calculation is performed through JavaScript in your browser. The BMI calculation function does not contain a command that uploads or stores the measurements entered into the calculator.

The wider website may separately use hosting logs, analytics, cookies or advertising services. Review the main Privacy Policy and Cookie Policy .

Avoid entering personal or confidential information anywhere it is not required. This calculator needs only the measurement values shown in the form.

BMI Calculator Frequently Asked Questions

BMI Information Sources

The adult category ranges and medical limitations described on this page are supported by public guidance from the United States Centers for Disease Control and Prevention and the World Health Organization.