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BMI Calculator

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Accepted BMI Ranges for Different Groups of People

GroupBMI Range
Women18.5 – 24.9
Men18.5 – 24.9
Children (2-18 years)according to age and sex, refer to pediatrician
Elderly (65+)22 – 27
This table shows the accepted range of body mass index (BMI) for different groups of people based on their sex, age, and general health condition. It should be used as a guide only and a healthcare professional should be consulted for a diagnosis of being underweight or overweight.

The Body Mass Index (BMI) Calculator can determine a person’s age-adjusted BMI and corresponding weight status. To convert units into either US or metric units, use the “Other Units” tab or the “Metric Units” tab for the International System of Units. Notably, the calculator also determines the Ponderal Index in addition to BMI both are covered in more detail below.

What is BMI?

The Body Mass Index (BMI) is a measurement of a person’s leanness or corpulence based on height and weight, and it is used to quantify tissue mass. It is commonly used to determine whether a person has a healthy body weight for their height. Specifically, the BMI calculation result is used to determine whether a person is underweight, normal weight, overweight, or obese based on where the value falls within a given range. These BMI ranges vary by region and age, and are sometimes further subdivided into subcategories such as severely underweight or severely obese. Even though BMI is a flawed indicator of healthy body weight, it can be used to determine whether further testing or treatment is necessary. Being overweight or underweight can have significant negative effects on one’s health. The various BMI-based categories that the calculator uses are shown in the table below.

How to use BMI Calculator?

Although BMI can be used as a screening tool, it cannot determine a person’s health or level of body fat. A healthcare professional conducts additional evaluations to determine whether BMI poses a health risk. Measurements of skinfold thickness, and analyses of diet, exercise, and family history are a few examples of these evaluations.

BMI Calculator

What is the BMI calculation method?

Both adults and children have the same BMI calculation methods. The following formulas are used in the calculation:

Measurements Unit Formula 
Kilograms and Centimeters BMI Formula = weight (kg) / [height (m)2
BMI is calculated using the metric system, which divides weight in kilograms by height in meters squared. Height is typically measured in centimeters, so divide the centimeters value by 100 to get the equivalent height in meters. Eg :  Weight = 68 kg, Height = 165 cm (1.65 m)
Calculation: 68 kg / (1.65 x 1.65) m2  = 24.98
Inches and Pounds BMI Formula = 703 x [ weight (lb) / [height (in)2
Weight in pounds (lbs) divided by height in inches (in) squared is multiplied by a conversion factor of 703 to determine body mass index (BMI). Example: Weight = 150 lbs, Height = 5’5″ (65″)
Calculation: 703 x [ 150 ÷ (65)2 ] = 24.96
BMI Calculation Formula

What are the risks of obesity?

The risk of several serious diseases and health issues rises with weight gain. According to the Centers for Disease Control and Prevention (CDC), the following risks are listed:

  1. Elevated blood pressure
  2. Diabetes Type II
  3. Cardiovascular disease
  4. Stroke
  5. A gallbladder illness 
  6. Higher levels of the generally regarded “bad cholesterol,” LDL, lower levels of the generally regarded “good cholesterol,” HDL, and higher levels of triglycerides
  7. The joint disease is known as osteoarthritis, is brought on by the destruction of joint cartilage
  8. Issues with breathing and sleep apnea
  9. Specific cancers such as endometrial, breast, colon, kidney, gallbladder, and liver
  10. Poor standard of living
  11. Clinical depression, anxiety, and other mental illnesses
  12. Body aches and difficulty performing some physical tasks
  13. Generally speaking, a higher mortality risk in comparison to people with a healthy BMI

The list above demonstrates the wide range of detrimental and occasionally fatal effects that being overweight may have. Ideally, a person should consult their doctor to determine whether or not they need to make any changes to their lifestyle in order to be healthier. Generally, a person should try to maintain a BMI below 25 kg/m2.

What are the risks connected to being underweight?

There are risks associated with being underweight, which are listed below:

  1. Vitamin deficiencies, anemia, and poor nutrition (lowered ability to carry blood vessels)
  2. Osteoporosis is a condition that weakens bones and raises the risk of breaking a bone.
  3. A decline in immune response
  4. Issues with growth and development, particularly in kids and teenagers,
  5. Hormonal imbalances that may affect a woman’s ability to conceive because they can interfere with her menstrual cycle. Additionally, the likelihood of miscarriage in the first trimester is higher in underweight women.
  6. Surgery-related complications that could occur
  7. Generally speaking, a higher mortality risk in comparison to people with a healthy BMI

Being underweight is occasionally a symptom of a disease or underlying condition, such as anorexia nervosa, which carries its own risks. If you believe you or someone you know is underweight, talk to your doctor immediately, especially if the cause does not seem obvious.

Ponderal Index

The Ponderal Index (PI), like BMI, measures a person’s leanness or corpulence based on their height and weight. The main distinction between the PI and BMI is that the height is cubed rather than squared in the formula (provided below). While BMI is a useful tool for determining leanness or corpulence in large populations, it is not reliable for determining leanness or corpulence in individuals. Although the PI suffers from similar issues, it is more reliable for use with very tall or short people, whereas BMI tends to record unusually high or low body fat levels for those at the extreme ends of the height and weight spectrum.

BMI’s Limitations

BMI has its limitations even though it is a popular and helpful indicator of healthy body weight. BMI is only a rough estimate and cannot account for body composition. Because there are many different body types and variations in muscle, bone, and fat distribution, BMI should be used in conjunction with other measurements rather than as the only way to establish a person’s healthy body weight.

  • In Adolescents and children:

Children and adolescents can also be affected by the same factors limiting BMI effectiveness in adults. Height and the degree of sexual maturation can also affect children’s BMI and body fat. In contrast to overweight children, whose BMI may be caused by higher levels of either fat or fat-free mass, obese children’s BMI is a better indicator of excess body fat than it is for overweight children all body components except for fat, which includes water, organs, muscle, etc. Their body fat-free mass may also cause the difference in BMI in thin children.

Nevertheless, for 90 95 percent of the population, BMI is a reliable indicator of body fat and can be used with other metrics to help determine a person’s healthy body weight.

  • In Adults

Because BMI measures excess body weight rather than excess body fat, it cannot be completely accurate. Age, sex, ethnicity, muscle mass, body fat, level of activity, and other variables all impact BMI. For instance, an older adult with a healthy weight who is completely passive in daily life may have a lot of excess body fat despite not being overweight. In contrast, a younger individual with a higher muscle composition and the same BMI would be considered healthy. It is entirely possible that athletes, especially bodybuilders who would be considered overweight because muscle weighs more than fat, are actually at a healthy weight for their body composition. According to the CDC, typically:

  • With the same BMI, older adults typically have more body fat than younger adults.
  • Women typically have more body fat than men for an equivalent BMI.
  • Due to their large muscle mass, athletes and those who are muscular may have higher BMIs.

What is a BMI percentile, and how is it used?

Following BMI calculation for kids and teenagers, the result is expressed as a percentile that can be found on a graph for boys and girls or by using a percentile calculator. These percentiles represent a child’s BMI compared to US kids who participated in national surveys between 1963–1965 and 1988–1944. During a child’s growth and development, weight, height, and their relationship to body fat all change. Therefore, it is necessary to interpret a child’s BMI about other kids of the same sex and age.

What other metrics exist in addition to BMI to measure excess body fatness?

Aside from using BMI calculators other techniques for determining body fatness include calipers to measure skin-fold thickness, underwater weighing, bio-electrical impedance, dual-energy x-ray absorptiometry (DXA), and isotope dilution. However, these techniques aren’t always easy to find, and they’re expensive or require highly skilled personnel. Additionally, many of these techniques can be challenging to standardize across observers or machines, making it more difficult to make comparisons between studies and time periods.

Who must avoid using a BMI calculator?

Bodybuilders, long-distance runners, expectant mothers, the elderly, and young children are not included in the BMI calculations. This is so because BMI only considers the number and ignores whether the weight is made up of fat or muscle. Athletes and people with higher muscle mass may have high BMIs without necessarily having higher health risks. A person’s BMI may be lower if they have less muscle mass, such as growing children or elderly people who may be losing some muscle. Using BMI is inappropriate because a woman’s body composition changes during pregnancy and lactation.

Is the BMI reliable?

Body Mass Index, or BMI, is a measurement of how much you weigh in relation to your height. Since being overweight or obese significantly raises your risk of developing a number of medical conditions, such as type 2 diabetes, heart disease, and cancer, accurate assessments of obesity are crucial. As rates of overweight or obesity rise, attention has turned to BMI and its limitations as a gauge of an individual’s ideal weight rather than that of entire populations where “averages” apply.

BMI provides a reliable estimate of weight-related health risks for most adults. Regardless of the factors below, if your BMI is over 35, your weight is definitely endangering your health. However, there are some circumstances where BMI in the 25–35 BMI range may under or overestimate these risks. Principally, they are:

  • Children

Your doctor or health visitor can explain your child’s position on the “centile charts,” which are used to project healthy weights for children.

  • Expecting mothers

The standard BMI calculations do not apply to pregnant women. 

  • If you have a lot of muscle mass, 

your BMI will assume that you have an average amount of body fat, including “intra-abdominal fat,” which is located deep within your stomach cavity rather than beneath your skin. Compared to fat under the skin, intra-abdominal fat is significantly more closely associated with risks of type 2 diabetes and heart disease.

  • If you have Asian ancestry

Asian-origin individuals are more likely than Caucasian individuals to develop intra-abdominal fat, which is fat that is deep within the stomach cavity rather than under the skin. People who experience this pattern of weight gain are referred to as “apples” rather than “pears” due to the shape of their bodies. As a result, because intra-abdominal fat is directly associated with the onset of heart disease and type 2 diabetes, their health risks begin to increase at a lower BMI. After reviewing the data, the World Health Organization decided against changing the cut-off points because of the variation in Asian populations. However, it suggests that for public health purposes, some Asian groups should be classified as overweight if their BMI is between 22 and 25 and obese if their BMI is between 26 and 31.

  • Senior citizens (over 65, possibly over 60)

BMI may not be a reliable indicator of body fat if you’re over 60 because muscle mass tends to decline, and body fat tends to increase in older people. If you have a lot of muscle, your body fat percentage might be lower than what your BMI suggests. But only those who exercise vigorously much more than average can claim this.

What are the ranges of BMI?

  • BMI Calculator for Men

You can use this calculator to calculate BMI for men’s U.S. units. (Weight in pounds ÷ height2 in inches) x 703 = BMI (For example: (150 pounds ÷ 65 inches2 ) x 703 = 26.6).

Metric units. Weight in kilograms ÷ height2 in meters = BMI (70 kilograms ÷ 1.7 meters2 = 24.2).

  • BMI chart for Men

According to health experts, BMI of 18.5 to 24.9 is considered healthy for men and people with AMAB. The same is true for women and people with AFAB. Check the BMI chart below for your weight classification.

BMIWeight classification
Below 18.5Underweight
18.5 – 24.9Normal
25.0 – 29.9Overweight
30.0 or higherObesity
BMI Chart for Men
  • BMI Calculator for Women

A moderate BMI for women is considered to be 18.5 to 24.9 by doctors. A BMI of 30 or higher may indicate obesity.

  • BMI chart for Women

Knowing one’s BMI enables one to determine where one falls within the National Heart, Lung, and Blood Institute’s standard weight categories. 

BMIWeight standard
Below 18.5 kg/m2Underweight
18.5 – 24.9 kg/m2Normal weight
25.0 – 29.9 kg/m2Overweight
30.0 and higherObesity
BMI Chart for Women
  • BMI for Children

Based on CDC growth charts, this calculator calculates body mass index (BMI) and the corresponding BMI-for-age percentile for kids and teens 2 through 19 years old. The results of this calculator might slightly deviate from BMI-for-age percentiles calculated by other programs due to possible rounding errors in age, weight, and height.

Having your child’s pediatrician take a measurement and share the results with you is the best way to learn their BMI percentile. How you can establish and encourage healthy habits at home will be discussed with you by your child’s pediatrician.

  • BMI chart for Children
Method Example 
Multiply their weight (in pounds) by 703184 × 703 = (A) 129,352
Multiply their height (in inches) by itself69 × 69 = (B) 4,761
Divide (A) by (B)129,352 ÷ 4,761 = 27.2 (BMI Score)
BMI Chart for Children

4. BMI for Senior Citizens

WHO defines an older person as someone 65 or older (sometimes 60 years or older). A healthy weight was established as a BMI between 23 and 29.9 kg/m2 based on extensive research, which established various BMI categories for older adults. This results from the discovery by researchers that a BMI between 23 and 33 is associated with a markedly elevated risk of mortality.

  • BMI Chart for Senior Citizens 
BMI RangeWeight status
< 23 kg/m²Underweight
23 – 29.9 kg/m²Normal
> 29.9 kg/m2Over weight
BMI Chart for Senior Citizens

Things to Improve BMI

Your BMI is heavily influenced by the foods you consume. Eating fruits, vegetables, and whole grains; lean proteins like fish, eggs, and beans; and healthy fats like olive oil can all help you lose weight.

Avoiding processed foods with added sugar, salt, and fat may also aid in weight loss. Sugary drinks are especially dangerous because they cause weight gain while providing no essential nutrients.

Finding an eating plan that works for you can be difficult because different things work for different people. Limit or monitor your consumption of the following:

Alcohol: Alcohol can cause weight gain and make it difficult for your liver to metabolize fat.

Salt: Too much salt promotes water retention, making you appear heavier than you are.

Also, try to move more! Walking or biking instead of driving, taking the stairs instead of the elevator, and pacing around the house while talking on the phone or talking to someone will all help!

You may have also heard that many overweight people do not get enough sleep. This is due in part to the fact that a lack of sleep can lead to weight gain and in part to the fact that obesity can cause sleep problems. To keep your BMI within a healthy range, ensure you get plenty of rest at night.


1. How precise is BMI?

BMI is intended to be used as a general guideline rather than an exact measurement. Because BMI only takes into account height and weight, it may not accurately reflect your body fat percentage. BMI, for example, does not consider muscle mass or age.

2. Does the BMI indicate how much weight needs to gain or lose?

You will need to be measured by a professional if you want to know if you are on track with your fitness goals. The method used to calculate your body fat percentage will affect the process. Calipers and scales are two common methods. Calipers are used to measure skinfold thickness, whereas scales are used to measure electrical resistance, also known as bioelectrical impedance analysis (BIA).

3. Is it possible to use BMI during pregnancy? How about during the lactation period?

When pregnant or breastfeeding, BMI may be inaccurate. If you are concerned about your weight, you should consult a medical professional to see if you need to change your lifestyle to improve your health.

4. Are there any measurements comparable to BMI that I can use?

Various tools can be used to assess or estimate body fat levels. Underwater weighing and bioelectrical impedance analysis are two of the most common methods (BIA). Because many studies have shown that BMI is highly correlated with body fat levels, BMI is widely regarded as a low-cost, simple, and effective screening method for overweight and obesity.

5. Is BMI usable for Kids?

For children and teenagers, BMI is age and gender-specific and is sometimes referred to as BMI-for-age6. A high level of body fat in children can lead to obesity and other health issues. Being underweight can put you at risk for several health issues. A high BMI indicates that you have a lot of fat on your body. Although BMI does not directly measure body fat, it is linked to more direct measurements of body fat.


The ratio of a person’s height to weight, which contrasts the weight of their organs, muscles, and bones with their body fat percentage, is known as their body mass index. A rising BMI will signal a higher body fat percentage. The main goal of our project was to create a tool that could calculate a person’s BMI and automatically determine their height and weight. A modern, elegant, electronic, and most importantly, “accurate” medical device, our Automatic BMI Calculator was designed to measure a person’s height and weight in under a minute.


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