BMI Calculator - Accurate Body Mass Index Tool For All Ages

What is a BMI Calculator?

A BMI calculator is a tool for determining a person's body weight based on their weight, height, and age. We offer a free online BMI calculator that you can access from any device, smartphone, tablet, or computer. Get your BMI value quickly to determine your weight status. Understand whether your body weight falls into the normal weight, overweight, underweight, or obesity category.

How to Use Our BMI Calculator?

Follow 5 easy steps and use our BMI calculator:

First, Choose Age stage from either adults or Teens/kids.
Second, you will choose a gender, male or female.
Next, write down your age, weight, and height.
Click on Calculate button.
And get the results.

Important note: Click on double arrow buttons to convert your height or weight into different metrics units such as cm, lbs, inches, etc.

What is BMI?

BMI (Body Mass Index) measures a person’s leanness based on height and weight. This value helps you quantify tissue mass. BMI is a popular index used to understand whether a person has a healthy weight based on height and age. Value from the BMI index helps you categorize a person as underweight, overweight, obese, or normal weight. BMI value may change based on age and region, and further subcategories of underwritten and obese are severely obese or severely underweight. If you are underweight, overweight, or obese, then this weight severely affects your health. It's good to know that the BMI value is imperfect, but it's still useful as a base test or indicator that requires physicians to take additional tests.

BMI Formula:

In Metric Units:

BMI = weight (kg) / {height (m) x height (m)}

In Imperial Units:

BMI = (weight (lb) / {height (in) * height (in)} x703

Here’s how to use each formula:

Metric Units:

Measure your weight in kilograms (kg).
Measure your height in meters (m).
Square your height by multiplying it by itself (height * height).
Divide your weight by the squared height to get your BMI.

Imperial Units:

Measure your weight in pounds (lb).
Measure your height in inches (in).
Square your height by multiplying it by itself (height * height).
Divide your weight by the squared height.
Multiply the result by 703 to get your BMI.
It’s important to use the appropriate units to calculate your BMI accurately.

When should BMI be used?

BMI should be used when you are overweight or obese. A BMI calculator will help you keep track of your body weight and take the necessary actions to prevent risks related to more body fat.

Why is the BMI important?

BMI is important because it helps determine whether you are overweight, underweight, or obese. Low and high body fat are associated with health risks, so keeping track of BMI enables you to take the required actions to prevent health risks.

Why use BMI instead of weight?

BMI should be used instead of weight as this tool is free to use, offers quick value, and can be accessed quickly on our website. All you need to do to use our free BMI calculator is plug in your weight and height and get a BMI value as quickly as you want.

BMI Table for Adults

Women and men aged 20 or older can use this BMI table as a reference to check their BMI values. This table is recommended by the World Health Organization's (WHO).

Get table and chart idea from here:https://www.calculator.net/bmi-calculator.html

BMI Chart for Adults

This BMI graph provides details of categories defined through the World Health Organization data.

**BMI Table for Children and Teens aged 2-20 years **

When you are going to use a BMI calculator to get values for children and teens aged between 2 and 20, you should use this BMI table for children; it is recommended by the Centers for Disease Control and Prevention (CDC).

BMI chart for children and teens aged 2-20

Here are age-percentile growth charts recommended by the Centers for Disease Control and Prevention (CDC)

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Limitations of BMI

The BMI Calculator is helpful as values from this calculator help determine healthy body weight. However, the Body Mass index does not consider overall body composition, such as bone mass, muscle, and fat. It’s vital to evaluate body composition while determining the healthy body weight of a person through BMI.

Limitation of BMI in Adults:

Body Mass Index (BMI) measures excess body weight instead of body fat. It is usually affected by activity level, sex, age, ethnicity, and muscle mass.

Here are some points to keep in mind:

Older adults usually have more body fat than younger people with the same BMI.

Women usually have more body fat than men, even when they have the same BMI value.

A muscular individual may be obese or overweight due to significant muscle mass.

Limitations of BMI in Children

The BMI values of children and adolescents also don’t consider their body composition. Height and level of sexual maturation may affect body fat and BMI values among children.

BMI is a better indicator for obese children than for overweight children who may have a high value of BMI due to increased levels of fat or fat-free mass. Thin children may have a difference in BMI value because of fat-free mass.

Now you understand the disadvantage of using a BMI calculator: It's not always an accurate indicator of weight. However, it is an indicator of body fat for 95 percent of people and helps you determine a healthy body weight.

What Risks Overweight People Face?

If you are an overweight person, you are at risk of different diseases or health issues listed below as per the Centers for Disease Control and Prevention (CDC):

High blood pressure
Type II diabetes
Coronary heart disease
Stroke
Gallbladder disease
Osteoarthritis
Sleep apnea and breathing issues
Higher levels of LDL cholesterol/lousy cholesterol
Lower levels of HDL cholesterol
High levels of triglycerides
Certain cancers (endometrial, breast, colon, kidney, gallbladder, liver)
Low quality of life
Mental issues such as clinical depression, anxiety, and others
Body pains and difficulty in performing some physical functions
High risk of mortality compared to those with a healthy BMI

The list mentioned above is super alarming for obese and overweight people. Doctors always recommend that individuals maintain their weight in a healthy BMI range below 25kg/m2. You need to change your lifestyle to fall under the healthy BMI range.

What Risks Do Underweight people face?

The list below is some health issues faced by underweight individuals:

Malnutrition
Anemia
vitamin deficiencies
Osteoporosis is a disease that leads to bone weakness and causes high bone breakage
A decrease in immune function
Growth and development issues in children and teenagers
Hormonal balances disrupt the menstrual cycle and lead to reproductive problems for women
High miscarriage chances in the first trimester
High risk of mortality

Sometimes, being underweight is due to a disease named anorexia nervosa, which also has some other health issues. Always consult your doctor after you know you are underweight after the BMI calculation.

BMI Formula with USI and SI Units

Here are some BMI formulas used in the International System of Units (SI) and the US customary system (USC). USC customary units use mass or weight in lbs/pounds and height in inches. On the flip side: International systems of Units for BMI calculation are weight in kg and height in meters.

BMI Formula in USC units= 703 x Mass (lbs)/height 2(in)

Let’s do a calculation for a person with 160 pounds weight and 5 feet 10 inches height into inches and it is 70 inches.

BMI Formula in USC units= 703 x 160/702=23

BMI Formula in SI= Weight (kg)/height2 (m)

Now we will convert 160 pounds into kg and it becomes 72.57 and convert 5 feet 10 inches into meters and it becomes 1.778 meters.

Let’s calculate BMI in SI= 72.57/ 1.778 2 = 23 

BMI Prime

BMI Prime is a ratio of an individual’s calculated BMI to the upper limit of BMI, which is considered a standard BMI value by institutions such as the WHO and the CDC. The upper limit varies in different countries but is usually 25 kg/m2. BMI Prime lets you quickly assess how much an individual’s BMI differs from a normal limit. It helps you compare different groups of people with different upper BMI limits.

The BMI prime formula

BMI Prime = BMI/25 `

BMI Prime is a dimensionless value as it is calculated by using a ratio of two BMI value- one value you calculate through our BMI calculator and another is BMI upper value that is equal to 25.

BMI Prime value less than 0.7 categorized as underweight
BMI Prime value from 0.74 to 1 is considered as normal
BMI Prime value more than 1 is considered as overweight
BMI Prime value more than 1.2 is classified as obese

Explore BMI Prime value chart for reference:

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What is the difference between the Ponderal Index and BMI?

The Ponderal Index (PI) is based on height and weight and lets you measure the corpulence of a person. However, this index is different from BMI.

The first difference between PI and BMI is their formula—the former cubes the height instead of squaring in meters. The second difference between the Ponderal Index and Body Mass Index is that BMI is useful for calculating the heights of large populations. At the same time, PI is a more reliable tool for estimating the heights of very tall or short individuals.

PI in Si, Metric units formula = weight (kg) /height(m)3 

PI in USC units = height (inches)/ 3√mass(lbs)

FAQs

How do I calculate my BMI?

You calculate BMI (Body Mass Index) by dividing the weight (kg) of an individual by his height (meters squared). For example, a person's weight is 70 kg, and height is 5 foot 7 inches. Convert height from inches to meters, 1.70 meters, while the square meters are 1.7x1.70 =2.89. Divide weight (kg) by height (2.89 meters squared) and get BMI =24.22 kg/m2.

At what age should you use BMI?

You should start using BMI for a 2-year-old kid. Doctors also rely on the BMI values of kids during routine checkups. BMI changes with age, and doctors use this calculation and compare it with standard gender-specific growth charts to determine your child's growth pattern.

What is the correct BMI for my age?

The correct BMW for your age depends on 18.5 to 24.9, which is a healthy weight range for young and middle-aged adults. If your BMI is under 18.5, you are underweight and malnourished. If your weight is 25 to 29.9, then you are overweight. Over 30 BMI is considered obese.

Is 45 kg underweight?

Yes, 45 kg for a 5'2" is underweight. The ss BMI is 18.29kg/m2 and underweight as per WHO Classifications.Is BMI for Age Accurate?

BMI is not an age-accurate measure of health, especially for adults over 65. It doesn’t tell the whole story about race, fitness, body composition, and age.

What is normal BMI?

Normal BMI is between 18.5 and 24.9 kg/m2.

What is better than BMI?

Waist circumference-to-height ratio (WHtR) is better than BMI because WHtR considers fat mass; it helps you predict fat mass and discriminate lean mass from childhood through young adulthood.

What is the weakness of BMI?

The weakness of BMI is that it accurately measures body fat content based on a person's height and weight since it doesn't consider overall body composition, muscle mass and bone density, sex differences, or race.

Is BMI a helpful tool?

Yes, BMI is a useful tool as it helps you predict obesity and the risks of chronic health issues. But it has some shortcomings. This tool does not take into account large amounts of muscle mass in athletes, and if they take their BMI values, then this value may categorize them as obese or overweight, which makes this tool inaccurate.

BMI Calculator- Calculate Body Mass Index Value