BMI Calculator
Use our interactive BMI calculator to track your health. Input your weight and height in either metric or US units to find your BMI, BMI Prime, and Ponderal Index.
BMI Calculator
kg
cm
| BMI Category | BMI (kg/m2) |
|---|---|
| Underweight | Less than 18.5 |
| Normal weight | 18.5–24.9 |
| Overweight | 25–29.9 |
| Obesity (Class 1) | 30–34.9 |
| Obesity (Class 2) | 35–39.9 |
| Extreme obesity (Class 3) | 40 and above |
Source: World Health Organization
How to Use the BMI Calculator
Remember, this calculator is a general guide to provide basic information. It may not accurately reflect the health status of every individual. Always consult with healthcare professionals for a more accurate health assessment.
- First, select the measurement unit of your preference from the dropdown menu labeled "Unit." You can choose between 'Metric' and 'US' units. If you select 'Metric', you'll enter your weight in kilograms (kg) and your height in centimeters (cm). If you select 'US', you'll enter your weight in pounds (lb) and your height in feet and inches.
- Next, select your gender from the dropdown menu labeled "Gender." You can choose between 'Male' and 'Female'.
- After you've selected your units and gender, enter your weight in the field labeled "Weight." Make sure to enter the weight according to the measurement unit you've selected.
- For your height, if you've selected 'Metric' units, enter your height in centimeters in the field labeled "Height." If you've chosen 'US' units, you'll see two fields for your height - one for feet and the other for inches. Enter your height in these fields.
- Once you've entered all your information, click on the "Calculate" button.
- The calculator will then display your results, including your Body Mass Index (BMI), the category your BMI falls into (such as Normal weight, Underweight, Overweight, etc.), the healthy weight range for your height, your BMI Prime, and your Ponderal Index.
Remember, this calculator is a general guide to provide basic information. It may not accurately reflect the health status of every individual. Always consult with healthcare professionals for a more accurate health assessment.
What is BMI?
Body Mass Index (BMI) is a simple tool that is generally used to estimate the total amount of body fat. It is a measure of your weight relative to your height. The BMI is an important indicator of healthy body weight and it can provide a ballpark figure of whether a person has the correct weight for their height.
Here is the standard BMI categories table:
| BMI (kg/m^2) | Weight Status |
|--------------|-----------------|
| Less than 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 and above | Obesity |
Although BMI can be a useful tool, it's important to know that it is not a diagnostic tool. It can't differentiate between weight associated with muscle and weight associated with fat. Because of this, people with a high muscle mass, like athletes, may have a high BMI but not be overweight or obese.
Furthermore, the distribution of fat matters. Excess fat in the abdominal area (as in "apple" body shapes) is associated with higher health risks than fat stored in the hips and thighs (as in "pear" body shapes).
It's also important to note that the BMI ranges are not age-specific for adults, which means they apply to adults of any age. However, the interpretation of BMI does vary among children and teens. For these age groups, BMI is both gender- and age-specific and is often referred to as BMI-for-age.
Women generally have more body fat than men. Therefore, they may have a slightly higher BMI but not be overweight. Age also plays a role in body fat. Older people may have more body fat than younger adults with the same BMI.
While BMI is a good general indicator of overall body fat, it should be used as a starting point rather than a standalone diagnostic tool for determining a person's healthy body weight. Always consider other factors and consult with healthcare professionals for a comprehensive health assessment.
Here is the standard BMI categories table:
| BMI (kg/m^2) | Weight Status |
|--------------|-----------------|
| Less than 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 and above | Obesity |
Although BMI can be a useful tool, it's important to know that it is not a diagnostic tool. It can't differentiate between weight associated with muscle and weight associated with fat. Because of this, people with a high muscle mass, like athletes, may have a high BMI but not be overweight or obese.
Furthermore, the distribution of fat matters. Excess fat in the abdominal area (as in "apple" body shapes) is associated with higher health risks than fat stored in the hips and thighs (as in "pear" body shapes).
It's also important to note that the BMI ranges are not age-specific for adults, which means they apply to adults of any age. However, the interpretation of BMI does vary among children and teens. For these age groups, BMI is both gender- and age-specific and is often referred to as BMI-for-age.
Women generally have more body fat than men. Therefore, they may have a slightly higher BMI but not be overweight. Age also plays a role in body fat. Older people may have more body fat than younger adults with the same BMI.
While BMI is a good general indicator of overall body fat, it should be used as a starting point rather than a standalone diagnostic tool for determining a person's healthy body weight. Always consider other factors and consult with healthcare professionals for a comprehensive health assessment.
What is BMI Prime?
BMI Prime is a dimensionless number independent of units. It is an index derived from the BMI and gives a straightforward way to compare the numbers without needing to think about units. The BMI Prime is simply the BMI value divided by 25 (the upper limit of the 'normal' range).
The beauty of BMI Prime is that it tells you what proportion of the maximum healthy weight you are currently at. For instance, a BMI Prime of 1.0 signifies that you are at the upper limit of the normal weight range. In other words, you are 100% of the maximum healthy weight for your height.
Similarly, a BMI Prime less than 1 indicates that the person is underweight; a value over 1 indicates that the person is overweight. A BMI Prime over 1.2 or 1.3 would imply moderate to severe overweight, respectively.
However, like BMI, BMI Prime should also be used judiciously. It is a simple tool that doesn't account for differences in muscle mass, fat distribution, and the varying proportions of body components among individuals. Therefore, it should not be the only tool to assess a person's weight and associated health risk, but used as one of the several tools that can give you a more complete picture.
Healthcare professionals might use BMI Prime as a more intuitive way to explain the BMI numbers to patients, as it can be easier for people to understand a percentage of the maximum healthy weight, rather than arbitrary divisions on a scale.
The beauty of BMI Prime is that it tells you what proportion of the maximum healthy weight you are currently at. For instance, a BMI Prime of 1.0 signifies that you are at the upper limit of the normal weight range. In other words, you are 100% of the maximum healthy weight for your height.
Similarly, a BMI Prime less than 1 indicates that the person is underweight; a value over 1 indicates that the person is overweight. A BMI Prime over 1.2 or 1.3 would imply moderate to severe overweight, respectively.
However, like BMI, BMI Prime should also be used judiciously. It is a simple tool that doesn't account for differences in muscle mass, fat distribution, and the varying proportions of body components among individuals. Therefore, it should not be the only tool to assess a person's weight and associated health risk, but used as one of the several tools that can give you a more complete picture.
Healthcare professionals might use BMI Prime as a more intuitive way to explain the BMI numbers to patients, as it can be easier for people to understand a percentage of the maximum healthy weight, rather than arbitrary divisions on a scale.
What is Ponderal Index?
The Ponderal Index (PI), also known as the Rohrer's index, is another measurement that considers the distribution of weight in relation to height. It is similar to BMI but with a different calculation. Specifically, it is calculated as the weight in kilograms divided by the height in meters cubed (kg/m³). This makes it a more cubic measure compared to the BMI.
The Ponderal Index aims to provide a more accurate assessment of leanness or corpulence than BMI by accounting for the cubic nature of the human body. It is often used in pediatric and neonatal settings for assessing the proportional growth and health of newborns, where the distribution of weight and height can have more variance and significance.
Like other measures of body mass, the Ponderal Index is not a perfect tool. It also does not consider factors such as muscle mass, bone density, or fat distribution, which can vary greatly among individuals. Therefore, the Ponderal Index should be used in combination with other measures when assessing overall health and fitness.
For adults, the values of the Ponderal Index generally range from 10 to 20. Values below or above this range might indicate underweight or overweight conditions respectively. However, these are broad estimations, and it's crucial to note that the "normal" range can vary based on factors such as age, sex, and ethnicity.
The Ponderal Index is another useful tool for examining body mass and can provide a different perspective than the BMI. However, it is most effective when used alongside other measurements and assessments in order to get a comprehensive understanding of an individual's health.
The Ponderal Index aims to provide a more accurate assessment of leanness or corpulence than BMI by accounting for the cubic nature of the human body. It is often used in pediatric and neonatal settings for assessing the proportional growth and health of newborns, where the distribution of weight and height can have more variance and significance.
Like other measures of body mass, the Ponderal Index is not a perfect tool. It also does not consider factors such as muscle mass, bone density, or fat distribution, which can vary greatly among individuals. Therefore, the Ponderal Index should be used in combination with other measures when assessing overall health and fitness.
For adults, the values of the Ponderal Index generally range from 10 to 20. Values below or above this range might indicate underweight or overweight conditions respectively. However, these are broad estimations, and it's crucial to note that the "normal" range can vary based on factors such as age, sex, and ethnicity.
The Ponderal Index is another useful tool for examining body mass and can provide a different perspective than the BMI. However, it is most effective when used alongside other measurements and assessments in order to get a comprehensive understanding of an individual's health.
BMI FAQs
1. What is a healthy BMI?
- A healthy BMI for adults is typically considered to be between 18.5 and 24.9.
2. Does BMI change for men and women?
- The calculation for BMI is the same for both men and women. However, the interpretation of BMI can vary due to differences in body composition between genders.
3. Is BMI accurate for athletes?
- BMI may overestimate body fat in athletes and people with a muscular build. Athletes tend to have a higher proportion of muscle mass, which weighs more than fat.
4. Is BMI accurate for seniors?
- As we age, muscle mass tends to decrease and fat percentage increases. This can lead to a BMI in the normal range, even when a senior person has excess body fat.
5. Can children use the same BMI chart as adults?
- No, children and teenagers have their own BMI charts that take age and gender into consideration due to their ongoing growth and development.
6. Is it possible to have a normal BMI and still be unhealthy?
- Yes, it's possible. Normal BMI doesn't rule out risks related to unhealthy diet, physical inactivity, smoking, or other life choices.
7. Does BMI consider muscle mass?
- No, BMI doesn't distinguish between weight from muscle or fat. This is why some athletes may have a BMI that categorizes them as overweight despite being in peak physical condition.
8. Is a lower BMI always better?
- Not necessarily. While high BMI can indicate potential health risks, being underweight (BMI < 18.5) can also be associated with health problems.
9. Can I use BMI to track my progress when I'm losing weight?
- Yes, you can. While it isn't perfect, BMI can still be a useful tool for tracking changes in body mass over time.
10. Why do some professionals criticize the BMI scale?
- BMI doesn't consider factors such as muscle mass, bone density, and distribution of fat. Therefore, it may not accurately reflect an individual's health or fitness level.
11. Does BMI differ across different ethnic groups?
- Yes, some ethnic groups may have different body fat distributions and risks of health conditions at the same BMI.
12. What is a "morbidly obese" BMI?
- A BMI of 40 or more is often considered "morbidly obese", a term that denotes a level of obesity that's especially likely to lead to serious health complications.
13. Can BMI measure body fat directly?
- No, BMI is not a direct measure of body fat. It's a calculation based on weight and height that's used as an indicator of body fatness.
14. What should I do if my BMI is high?
- If your BMI is high, it's advisable to consult a healthcare provider. They can further evaluate your health risk using additional information and tests, and guide you about lifestyle changes or treatments.
15. Is BMI the only tool to measure body weight health risk?
- No, BMI is just one of many tools. Others include waist circumference, waist-to-hip ratio, body composition tests, and physical fitness assessments.
- A healthy BMI for adults is typically considered to be between 18.5 and 24.9.
2. Does BMI change for men and women?
- The calculation for BMI is the same for both men and women. However, the interpretation of BMI can vary due to differences in body composition between genders.
3. Is BMI accurate for athletes?
- BMI may overestimate body fat in athletes and people with a muscular build. Athletes tend to have a higher proportion of muscle mass, which weighs more than fat.
4. Is BMI accurate for seniors?
- As we age, muscle mass tends to decrease and fat percentage increases. This can lead to a BMI in the normal range, even when a senior person has excess body fat.
5. Can children use the same BMI chart as adults?
- No, children and teenagers have their own BMI charts that take age and gender into consideration due to their ongoing growth and development.
6. Is it possible to have a normal BMI and still be unhealthy?
- Yes, it's possible. Normal BMI doesn't rule out risks related to unhealthy diet, physical inactivity, smoking, or other life choices.
7. Does BMI consider muscle mass?
- No, BMI doesn't distinguish between weight from muscle or fat. This is why some athletes may have a BMI that categorizes them as overweight despite being in peak physical condition.
8. Is a lower BMI always better?
- Not necessarily. While high BMI can indicate potential health risks, being underweight (BMI < 18.5) can also be associated with health problems.
9. Can I use BMI to track my progress when I'm losing weight?
- Yes, you can. While it isn't perfect, BMI can still be a useful tool for tracking changes in body mass over time.
10. Why do some professionals criticize the BMI scale?
- BMI doesn't consider factors such as muscle mass, bone density, and distribution of fat. Therefore, it may not accurately reflect an individual's health or fitness level.
11. Does BMI differ across different ethnic groups?
- Yes, some ethnic groups may have different body fat distributions and risks of health conditions at the same BMI.
12. What is a "morbidly obese" BMI?
- A BMI of 40 or more is often considered "morbidly obese", a term that denotes a level of obesity that's especially likely to lead to serious health complications.
13. Can BMI measure body fat directly?
- No, BMI is not a direct measure of body fat. It's a calculation based on weight and height that's used as an indicator of body fatness.
14. What should I do if my BMI is high?
- If your BMI is high, it's advisable to consult a healthcare provider. They can further evaluate your health risk using additional information and tests, and guide you about lifestyle changes or treatments.
15. Is BMI the only tool to measure body weight health risk?
- No, BMI is just one of many tools. Others include waist circumference, waist-to-hip ratio, body composition tests, and physical fitness assessments.
