BMI (Body Mass Index) is a number calculated from a person's weight and height. BMI is a fairly reliable indicator of body fatness for most people. Additionally, BMI is an inexpensive and easy-to-perform method of screening for weight categories that may lead to health problems.
Your BMI is
What is BMI?
A person’s Body-Mass Index, or BMI, helps them check whether they’re a healthy weight for their height. If a person weighs less or more than the recommended weight for their height, it could lead to health issues in the future. While BMI is not the only factor individuals should consider while working on their health and fitness, it is a good starting point. To understand what your BMI is, you need to know your height and weight. You can then use an online BMI calculator to check your BMI, which will help you understand if you’re underweight, a healthy weight, overweight or obese. Or, you can measure your height in metres and weight in kilograms. Divide your weight by your height squared to calculate your BMI.
Underweight – BMI less than 18.5
Normal weight – BMI between 18.5 and 24
Overweight – BMI between 25 and 29.9
Obese – BMI above 30
- A BMI calculator is an online or offline device which measures your body mass index. The body mass index or BMI is a measure of how much body mass you have in relation to your height and weight.
- Body mass refers not only to the fat within your body but also within muscles and bones. It is calculated by taking your weight and dividing it by the square of your height. The BMI figures let you know whether you are within normal weight range, or if you are underweight or overweight.
- Both high BMIs and low ones are known to raise a host of health problems, especially as you age. However, a high BMI in itself is not always, medically speaking, a cause for alarm. It should be viewed in conjunction with other health parameters.
- To find out if your BMI or someone else’s BMI, the calculation process is simple. You can do this yourself by using a handheld calculator or do this online via websites or apps containing body mass index calculators.
- To arrive at the result yourself, you simply divide your weight in kilograms by the square of your height in metres. Or simply input your height and weight in an app or website and the BMI results will flash on your screen.
- If the numbers show that your BMI is above normal or below the normal range, you should get yourself checked by a doctor at least once every six months or at least once a year.
- A number between 18.5 to 25 kg/m2 is considered normal BMI. Less than 15 is classified as very severely underweight, from 15 to 18 is categorized as underweight, from 25 to 30 is considered overweight. From 30 to 40 is classified as obese and above 40 as very severely obese.
- Being overweight can lead to a host of health problems. If you are feeling sluggish or lacking energy, chances are that you have too much fat for your height and weight or comparatively less fat than what is recommended. Knowing what your BMI or body mass index is a good way to find out whether you are obese or underweight. Body mass index is thus basically an indicator of how much fat one’s body has depending on that person’s height and weight. The ideal BMI varies from person to person depending not only on height and weight but other factors too.
- Broadly speaking, irrespective of whether you are male or female, a BMI in the range of 18.5 to 24.9 is considered normal. Less than 18.5 is termed underweight. Over 24.9 to 30 considered overweight. Anything above 30 is categorised as obese. These figures apply across the board irrespective of ages as well. BMI is expressed in kg/m2. All you need here is common sense to know that if a person with a height of 4 feet has a BMI equal to that of a 6-feet individual, the shorter person’s BMI is clearly not ideal. Of late, there has been a consensus in the medical fraternity that the BMI cut off for Asian populations should be 23 since these populations have been found to be more vulnerable to diabetes. These indicates that there is no ideal BMI range for a gender category or even particularly for age ranges.
- The ideal BMI chart for men
|Weight in pounds (kgs in brackets)||Height in feet and inches|
|5 feet||5 feet, 3 inches||5 feet, 6 inches||5 feet, 9 inches||6 feet|
- Asking whether there is an ideal BMI for women is the same as asking whether there is an ideal BMI for men. There is no ideal range of BMI for a class of adult males any more than there is for adult females. Since BMI is a function of height and weight in relation to each other, what gender you belong to has little significance. BMI or body mass index is merely an indicator of how much fat you have in a certain amount of height. The BMI values of 18.5 to 24.9 as normal, less than 18.5 underweight, 25 to 29 overweight and above 29 as obese apply equally to men as well as women. A woman have a BMI of 35 is exposed to the same health risks as a man having a similar BMI.
- Women in general are said to have a higher percentage of body fat than men. This does not mean that there is a separate normal BMI value for men and women. This is also why women require less calories per unit of body weight as compared to men. Studies have shown that on average, men have slightly higher BMI values than women. But this difference increases with age as women tend to put on more weight as they grow older. Higher BMI cut offs for women like 30, 32 and 33 are considered normal by some studies. But it’s best to follow the consensus on what’s normal for both men and women.
- The ideal BMI chart for women
Weight in pounds (kgs in brackets)
Height in feet and inches
5 feet, 3 inches
5 feet, 6 inches
5 feet, 9 inches
- Calculating the ideal body weight or BMI for children differs from those used for adults. This is because the amount of body fat changes as children grow up.
- The accepted formula for calculating BMI in children is weight divided by the height in metres squared and the result multiplied by 703. Age and gender makes a significant difference in what makes the ideal BMI for children.
- In the case of children, the BMI of each child is matched against the percentiles for children of the same sex and age. Children with a BMI between the 85th and 95th percentile are considered overweight. Percentile is a measure that indicates how a child stands in comparison to a group having the same characteristics, such as a similar age and gender. A child whose BMI falls in the 85th percentile means that he/she weighs more than 85 percent of his/her age group.
- A BMI of 25 to 30 means you are overweight, a BMI from 30 to 40 means you are obese and above 40 severely obese.
- World Health Organisation statistics reveal that 33 per cent of the world’s adult population is overweight while 10 per cent are obese.
- There is a higher probability that being overweight itself can lead to a lot of health problems. Your general well-being is affected once your BMI ranges anywhere from 30 and above. These problems are manifested in conditions like high blood pressure, heart disease and stroke, diabetes, gall bladder disease and gallstones, osteoarthritis, gout, sleep apnea and other breathing problems.Although not everyone fat or obese has health issues, there is a higher chance that you may suffer from these conditions if you have a family history where anyone or both of your parents have suffered from either of the above conditions.
- Being underweight is just as bad as being overweight. A BMI of 15 to 16 puts you in the underweight category. Anything less than 15 is considered severely underweight.
- While being overweight is one extreme of the BMI scale, underweight is the other extreme. Being underweight indicates that you are most likely malnourished or suffer from low immune function or osteoporosis.
- Being underweight can also expose you to surgical complication risks and in the case of women, lead to fertility issues due to irregular menstrual cycles. Underweight children can encounter growth and development issues.
- There are studies showing that women who are underweight are more prone to suffering from depression than those women who are at an ideal weight.
Is BMI Reliable?
Your BMI helps measure how appropriate your weight is for your height. While some people might be naturally broader, the BMI range allows for these discrepancies. The BMI measure works to help you understand whether you fall under the normal weight, overweight or obese category. People who carry extra weight, especially around their stomach, are prone to developing lifestyle diseases such as diabetes, cancer or heart issues. For adults, the BMI offers a good estimate of weight-related health problems.
Most often, physicians accurately measure your height and weight and use your BMI to understand your future health risks. If your BMI is higher than it should be, they will likely recommend some kind of diet and exercise regime to bring your weight down.
A person’s Body-Mass Index, or BMI, helps them check whether they’re a healthy weight for their height. If a person weighs less or more than the recommended weight for their height, it could lead to health issues in the future. While BMI is not the only factor individuals should consider while working on their health and fitness, it is a good starting point. To understand what your BMI is, you need to know your height and weight. You can then check your BMI against the BMI chart:
The numbers on the chart will help you understand if you’re underweight, a healthy weight, overweight or obese.
Underweight – BMI less than 18.5
Normal weight – BMI between 18.5 and 24
Overweight – BMI between 25 and 29.9
Obese – BMI above 30
Researchers have divided obesity into three categories:
Class I – BMI 30 to 34.9
Class II – BMI 35 – 39.9
Class III – BMI 40+
To arrive at your BMI figure, you need to know your weight in kilograms and your height in metres. If you know what your height is in centimetres, you can simply divide that number by 100. To calculate your BMI, you need to divide your weight in kilograms by your height in metres squared.
If you know what your weight is in pounds and what your height is in inches, you can still calculate your BMI. You need to divide your weight in pounds by your height in inches squared. You then need to multiply the amount by 703.
You can also use our BMI calculator to quickly find out your BMI. Simply input your height and weight to find out your BMI instantly.
BMI for Kids
Your child’s body develops and changes rapidly. This is why a standard adult BMI chart will not work. Instead, to keep track of whether your child is the correct weight for their height, doctors use another chart. They start with a standard BMI calculation based on your child’s height and weight. The BMI value is then used to determine how your child compares to other children of the same age and gender. This is done with the help of percentages and percentiles. The weight categories for children, based on percentiles, are:
Underweight – BMI less than the 5th percentile
Normal Weight – BMI above the 5th percentile but lower than the 85th percentile
Overweight – BMI above the 85th percentile but lower than the 95th percentile
Obese – BMI greater than or equal to the 95th percentile
Limitations of an Online BMI Calculator
Despite its popularity, BMI figures do have certain drawbacks when it comes to predicting future health issues. Your BMI only uses your height and weight and it does not take your body composition into account. So, the distribution of your muscle and bone mass might increase your BMI even if you’re very healthy and not likely to suffer from weight-related health issues in the near future. Let’s take a closer look at the limitations of using BMI for various age groups:
BMI is not considered accurate since it only measures excess body weight instead of excess body fat. So, it’s a good idea for adults to use BMI along with other measures to understand their future health risks. The drawbacks of using BMI for adults include:
- Older adults will likely have more fat than younger individuals who have the same BMI.
- Women are more likely to have more body fat than men who have an equivalent BMI.
- Athletes and muscular people will probably have a higher BMI than others since they have large muscle mass.
Young Adults and Children
BMI cannot take into account a child’s growth rate and maturity. Typically, BMI can be used to identify obese children, but not overweight children as a slightly higher BMI could be caused by increased fat-free mass.
Despite the slight discrepancies, it’s possible to use BMI to accurately indicate the body fat of around 90% of the population.
Alternate Estimates of Weight-Related Health Risks
As we have seen above, BMI may not always be 100% accurate. So, there are a few other ways in which you can estimate whether you are overweight or obese and how that can affect your health. Here are some other ways you can check on your health:
- Waist Circumference
You need to measure the circumference of your waist. Find the halfway point between the bottom of your ribcage and the top of your hips, measure along this point with the measuring tape, parallel to the floor. Ensure you are breathing out when you measure. For men, a circumference higher than 94 centimetres is associated with an increased health risk. Anything higher than 102 centimetres indicates a high health risk. Women face an increased health risk if their waist circumference is over 80 centimetres and a high health risk if it is over 88 centimetres.
- Waist to Hip Ratio
Another good way to understand your health risk is by checking your waist to hip ratio. Start by using the method mentioned above to measure your waist circumference. To measure your hip size, make sure you place the measuring tape around the widest part of your hips. You need to divide your waist circumference by your hip measurement to get the ratio. For men, a hip ratio higher than 1, can indicate a greater than average risk of health issues. For women, a hip ratio higher than 0.85 is associated with a greater than average health risk.
- Waist to Height Ratio
During a study, researchers compared different methods to identify health risks. They checked BMI, waist circumference, waist to hip ratio and waist to height ratio. They found that the waist to height ratio was more accurate in predicting whole-body fat levels than any other calculation method. You can start by measuring your waist circumference and then measuring your height. Ensure that you use the same unit of measure for both. Divide your weight circumference by your height to get your ratio. A ratio of 0.53 or more for men indicates whole body obesity. A ratio of 0.54 or more in women also indicates whole body obesity. A ratio of 0.59 or more indicates abdominal obesity.
BMI Calculator - FAQs
BMI or body mass index is a measure of how much body mass an individual has according to his weight and height. To calculate your BMI, simply divide your weight in kilograms by your height squared in metres. You can also find the results instantly by entering the height and weight data in online BMI calculators. BMI is not always an appropriate indicator of a person’s health. Growing children and elderly people may have less muscle mass and therefore lower weight, thus lowering their BMI. On the other hand, athletes may have higher BMI as they put on plenty of muscle from exercise.
The BMI formula is quantified as kg/m2 for most adults, irrespective of gender. The formula that uses kilograms and meters is called a metric BMI formula while the one that uses pounds and inches for measurement is called the imperial BMI formula. The BMI score chart is applied to adults aged 20 and above. A BMI between 18.5 and 25 is considered normal, between 25 and 30 overweight, between 30 to 35 fat, and between 35 and 40 too fat. BMI should preferably be measured first thing in the morning before breakfast, the time when your weight is most accurate.
Maintaining a healthy body weight is important for everyone. According to the Center for Disease Control, men who have a BMI of 30 and above are obese, between 18.5 and 25 are considered normal, those with BMI below 18.5 are labelled underweight and those with BMI between 25 and 29 are considered overweight. As a thumb rule, taller men should weigh more than shorter guys, generally 2 to 4 points more per inch of height. The tendency to put on weight also increases with age, even though height, body frame and gender play crucial roles in determining your BMI levels.
The ideal, overweight, underweight and obese BMI ranges for men and women are the same with only minor differences. A National Institute for Health, USA study found that women who had never smoked but were overweight had a 13 per cent increased chance of dying, than those with a BMI between 22.5 and 24.9. Women who are obese or severely obese had significantly higher chances of dying early. Researchers saw a 44 per cent rise in risk of death for participants with BMI of 30 to 35 and an 88 per cent upside in risk for those with a BMI of 35 to 40, followed by a 250 per cent higher risk of dying for women whose BMIs fell between 40 and 49.
BMI figures are responsive to changes in height but not to age. Maintaining a healthy BMI as you grow older becomes tough as due to a slowed metabolism you tend to put on more weight, mostly on the waistline. After 20 years of age, the height of a person becomes more or less settled. Weight therefore becomes the variable that you should take into account. It is alright for a taller person to weigh more than a shorter person. The guideline to follow here is irrespective of how old or how young you are, your BMI should fall within 18.5 and 25.
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