BMI Calculator

A BMI Calculator helps you estimate your Body Mass Index from your height and weight. BMI is a simple weight-to-height measurement that is commonly used as a starting point when assessing weight status in adults.

BMI can be calculated within seconds, which makes it useful when you want to check your result without doing the formula manually.

What Is BMI?

Body Mass Index (BMI) is calculated by comparing body weight with height. For adults, the standard BMI formula is:

BMI = weight in kilograms ÷ height in meters²

For example, an adult who weighs 70 kg and is 1.75 meters tall has a BMI of approximately 22.9.

If your measurements are in pounds and inches, the equivalent formula is:

BMI = weight in pounds × 703 ÷ height in inches²

How to Use the BMI Calculator

Enter your height and weight in the appropriate fields and select the correct units. If the calculator displays additional fields, follow the instructions provided for those fields.

For an accurate calculation:

• Enter your current height.
• Enter your current weight.
• Check that the selected units are correct.
• Make sure height and weight have not been entered in the wrong fields.
• Review the result after calculating.

Adult BMI Categories

For adults aged 20 and older, BMI is commonly grouped into four categories:

• Below 18.5: Underweight
• 18.5 to less than 25: Healthy weight
• 25 to less than 30: Overweight
• 30 or higher: Obesity

These ranges are general screening categories and should not be treated as a diagnosis. (CDC)

How Accurate Is BMI?

The mathematical BMI calculation is straightforward when the correct height and weight are entered. The more important limitation is how the result is interpreted.

BMI does not directly measure body fat. It also does not distinguish between muscle, bone and fat. For example, a person with a high amount of muscle may have a higher BMI even though their body-fat level may not be high.

For this reason, BMI is best considered alongside other relevant information such as body composition, waist circumference, physical activity, medical history and other health measurements. (CDC)

BMI for Children and Teenagers

Adult BMI categories should not be used for children and teenagers.

For people between 2 and 19 years old, BMI is interpreted using age- and sex-specific growth charts and percentiles. If you are checking BMI for a child or teenager, use a calculator designed specifically for that age group. (CDC)

What Can Affect the Interpretation of BMI?

The same BMI value can have different implications for different people. Factors that may be considered alongside BMI include:

• Muscle mass
• Body composition
• Age
• Waist circumference
• Physical activity
• Family and medical history
• Other health measurements

Looking at these factors can provide more useful context than relying on BMI alone.

Related Health Calculators

BMI is only one way to look at weight and body composition. Depending on what you want to understand, you may also find a BMR Calculator useful for estimating basal metabolic rate, a Body Fat Calculator for an estimated body-fat percentage, or an Ideal Weight Calculator for a general weight-range estimate.

Each calculator measures something different, so their results should not be treated as interchangeable.

When Should You Talk to a Healthcare Professional?

Consider discussing your BMI or weight-related concerns with a qualified healthcare professional if you are unsure how to interpret your result or if you are planning significant changes to your diet, exercise or weight.

A professional can consider your individual circumstances and other health measurements that a BMI calculation cannot capture.

Important Disclaimer

This BMI Calculator is provided for general informational and educational purposes. BMI is a screening measurement and does not directly measure body fat or diagnose a medical condition. The result should be considered together with other relevant health information and is not a substitute for professional medical advice, diagnosis or treatment.

Frequently Asked Questions

What does a BMI Calculator calculate?

A BMI Calculator calculates Body Mass Index using a person's height and weight and provides the corresponding adult BMI category when applicable.

What is a healthy BMI for an adult?

For adults aged 20 and older, a BMI from 18.5 to less than 25 is generally classified as the healthy-weight range.

Does BMI measure body fat?

No. BMI uses height and weight and does not directly measure body fat or body composition.

Is BMI calculated differently for men and women?

The standard adult BMI formula is the same for men and women. Adult BMI categories are based on the BMI value rather than separate ranges for men and women.

Can children use adult BMI categories?

No. Children and teenagers require age- and sex-specific BMI interpretation rather than the standard adult categories.

Disclaimer

This BMI Calculator is provided for general informational and educational purposes only. The results are estimates based on the information entered and should not be considered medical advice, diagnosis, or treatment. BMI is only one general measure of body size and may not accurately reflect body composition or health for every individual. For personalized health advice or concerns about your weight or health, consult a qualified healthcare professional.