BMI Calculator
BMI Calculator
Enter your height and weight to calculate your Body Mass Index.
What Is BMI?
Body Mass Index, commonly called BMI, is a simple screening calculation that compares your weight with your height. It gives adults a quick way to see which broad weight category their height and weight combination falls into.
BMI is useful because it is easy to calculate and does not require special equipment. However, it is only one health measure. A BMI number does not directly measure body fat and cannot tell the difference between weight from muscle, fat, bone, or other body tissues.
Measure Your Height
Use your current height without shoes. Choose Metric for centimetres or Imperial for feet and inches.
Enter Your Weight
Enter kilograms in Metric mode or pounds in Imperial mode. Using recent and accurate measurements improves the calculation.
How Is BMI Calculated?
The metric BMI formula divides a person's weight in kilograms by the square of their height in metres.
For example, if an adult weighs 70 kg and is 1.75 metres tall, the calculation is 70 ÷ (1.75 × 1.75), which gives a BMI of about 22.9.
The Imperial version uses weight in pounds and height in inches with the standard conversion factor of 703. The calculator above performs this automatically.
How to Read an Adult BMI Result
For adults aged 20 and older, the CDC uses four main BMI categories. These ranges are intended for screening and should be considered alongside other relevant health information.
| Category | Adult BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Healthy Weight | 18.5 to less than 25 |
| Overweight | 25 to less than 30 |
| Obesity | 30 or greater |
What BMI Can Tell You
BMI provides a quick weight-to-height screening value. It can be one useful piece of information when discussing weight status and general health with a healthcare professional.
What BMI Cannot Tell You
BMI does not directly measure body fat, muscle mass, fitness, nutrition, blood pressure, cholesterol, or a person's overall health.
Why BMI Does Not Tell the Whole Story
Two people can have the same BMI while having very different body compositions. For example, a person with substantial muscle mass may have a higher BMI even though the additional weight is largely muscle rather than body fat.
For individual health assessment, BMI may be considered together with other factors such as medical history, physical examination, blood pressure, cholesterol levels, lifestyle, and other measurements that a healthcare professional considers relevant.
Adult BMI categories should also not be used in the same way for children and teenagers. Because young people are still growing, their BMI is interpreted using age- and sex-specific percentiles. Pregnancy also changes body weight and should be assessed using appropriate prenatal care rather than a general adult BMI result alone.
What Should You Do After Calculating BMI?
If your result is outside the healthy-weight range, avoid treating the number as a diagnosis. It may be useful as a reason to look more closely at your overall health, eating pattern, physical activity, medical history, and other factors.
Likewise, a BMI within the healthy range does not guarantee that every aspect of your health is ideal. Regular healthcare, balanced nutrition, appropriate physical activity, adequate sleep, and other healthy habits remain important regardless of a single BMI result.
If your weight has changed unexpectedly, you are pregnant, you are under 20, or you have a health condition that affects weight or body composition, a healthcare professional can help you interpret the result in context.
BMI Calculator FAQs
What is considered a healthy BMI for adults?
For adults aged 20 and older, a BMI from 18.5 to less than 25 is classified by the CDC as the healthy-weight range.
Is BMI the same as body-fat percentage?
No. BMI uses only height and weight. It does not directly calculate the percentage of your body that is fat.
Can a muscular person have a high BMI?
Yes. Because BMI cannot distinguish muscle from fat, people with higher muscle mass can have a BMI that falls into a higher category.
Can children use this adult BMI calculator?
This adult category system is intended for adults aged 20 and older. Children and teenagers need BMI-for-age interpretation using age- and sex-specific percentiles.
Does BMI diagnose obesity or another medical condition?
No. BMI is a screening measure. Medical assessment may include BMI together with other health information.
Sources and Health Guidance
The adult BMI ranges and calculation guidance used on this page follow established public-health information from the U.S. Centers for Disease Control and Prevention and the National Heart, Lung, and Blood Institute.
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