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BMI Calculator

Body mass index calculator allows you to calculate BMI for adult men, women, children, or teens based on their weight to height ratio.

Height (ft)
Height (in)

What is BMI?

BMI (Body Mass Index) is the value derived from the height and weight of men and women. It is a widely used metric for categorizing a person as obese, overweight, average, or underweight. BMI is calculated in the units of kilogram per meter square, as it is measured by dividing the square of a body's height by a body mass. 

BMI Categories:

Generally, you can consider yourself one of them if your BMI falls between the given ranges:

  • Obese BMI = If it's equal to or greater than 30
  • Overweight = BMI is equal to or between 25 - 29.9
  • Normal Weight = BMI is equal to or between 18.5 - 24.9
  • Underweight BMI= Less than 18.5

About BMI Calculator

Avoid the hassle of manual calculation as SmallSEOTools has introduced the BMI calculator that provides accurate results using the BMI formula in a matter of instances. Calculate BMI value corresponding to weight status while taking age and height into consideration. This body mass index calculator is for men, women, and children. For children, BMI is presented as a percentile compared to children of the same age group and gender.

We have categorized BMI calculator into two portions:

1. For Adults (Women and Men)

The BMI between men and women varies as they don’t have identical body measures and genetics. On average, women are short-heightened; therefore, their BMI cannot be treated similarly to men. Our BMI Calculator for women and men allows you to check BMI distinctly. No need to go through any installation and registration process for using this body mass index calculator.

2. For Children

Genetics and body measures vary from person to person due to the difference in age ranges. Therefore, the Body Mass Index is interpreted differently for both adults and children. The BMI Calculator for children by SmallSEOTools has been designed to allow users to find their BMI as per their age range. Check BMI of your child to determine whether he is underweight, healthy, overweight, or obese. For BMI calculation you must know the age of your child. If you have any doubt about the exact age take assistance from an age calculator and get instant results. 

How to Calculate BMI for Adults?

The online BMI calculator is applicable for adults aged 20 years and above. Calculate your body mass index in either US or Metric units by following the steps given below:

  • Select Gender (Male, Female)
  • Enter your height in ft/in or Cm
  • Enter Weight in Lbs or KGs 
  • Now hit the “Calculate BMI” button

BMI Table for Adults


BMI Ranges 

Severe Thinness


Moderate Thinness


Mild Thinness

17 – 18.5


18.5 – 25


25 – 30

Obese Class 1

30 – 35

Obese Class 2

35 – 40

Obese Class 3


How to calculate BMI for Children and Teens?

The teen BMI calculator is designed for children or teens between 2 to 20 years old. Follow the steps given below to determine a child's BMI:

  • Choose the child and teen tab 
  • Then select your child's gender
  • Select the age
  • Enter height in ft/in or cm
  • Enter weight in lbs or kgs 
  • Hit the calculate button to get your child's BMI.

Risks Associated with Being Overweight

Being overweight leads a person to several health issues. You can face the following risks with being overweight:

  • High blood pressure
  • High LDL cholesterol
  • Heart disease
  • Type 2 diabetes
  • Breathing issues
  • Mental disorders
  • Anxiety
  • Depression
  • Body pain

Risks Associated with Being Underweight

Being underweight can also lead to medical problems, just like obesity. The significant risks you can face being underweight are:

  • Sickness
  • Anemia
  • Feeling tired
  • Slow growth
  • Premature birth
  • Irregular periods
  • Skin and hair problems 

How Do I Calculate BMI Manually?

There are two main formulas to calculate BMI, which are English BMI and Metric BMI. Let’s take a look at each of them and understand how they work with the help of an example. 

English BMI Formula:

= 703 x weight (lbs.)/ height2 (inches)

With this BMI formula, you need to multiply the weight in lbs. by 703 and divide it by the height squared in inches. For instance, if a person’s weight is 160 lbs. and height is 70 inches, then his BMI would be calculated as:

= 703 x 160/ 702

BMI = 22.9

Metric BMI Formula:

= Weight (Kgs)/ height2 (meters)

The metric BMI formula is similar to the English formula, but the only difference between them is the measurement units. If a person’s height is 1.8 meters and weight is 100 kg, then with the metric formula, his BMI would be calculated as:

= 100/1.82

BMI = 30.9

In the world of automation, people prefer to use an online BMI calculator for quick and hassle-free calculations.

Limitations of BMI

Experts have raised their fingers over the reliability of the Body Mass Index due to several reasons. There are certain limitations of BMI due to which they have termed it an inaccurate measure for analyzing body fat. Some of its limitations are:

  • BMI charts don't distinguish between the gender of the individuals. Males are prone to gaining muscle mass, whereas females have fat mass, which makes BMI an unrealistic measure.
  • BMI doesn’t take body fat percentage or muscle mass into account.
  • BMI doesn’t specify water weight and bone mass while calculating the relation between height and weight.

Who Shouldn’t Use a BMI Calculator?

BMI wouldn’t be an accurate representation for many people, such as pregnant women, athletes, young children, and bodybuilders. This is because a BMI calculator considers weight just as a number; however, for some people, the weight could be heavy due to muscles rather than fats.

For instance, athletes and bodybuilders have a high muscle mass that results in a much higher BMI. But this doesn’t mean they are open to facing health issues like obese people. Similarly, during pregnancy, the mass and body of a woman change, which makes the BMI calculator ineffective for them. Moreover, BMI calculation will show low BMI for children as they are likely to lose mass. But they shouldn’t be considered underweight as they are still at a growth stage.


  • When Should I Be Concerned with My Child's Weight?

If your child is losing weight, getting weak, staying ill for ample time, or has a lasting illness, you should be concerned and talk to your doctor.

  • When Should I Start Calculating BMI? How Often Should I Check?

You can start BMI calculation whenever you want. For children, it must be checked for the ones who are 2 years old. You can calculate your BMI once every four weeks.

  • What is a Healthy BMI?

The healthy BMI ranges from 18.5 to 24.9. Moreover, underweight BMI is less than 18.5, and overweight BMI ranges from 25.0 to 29.9.

  • What is My Ideal Weight?

Your ideal body weight depends upon your sex, age, and height. There’s no specific figure of ideal weight for all individuals.

  • Is Muscle Counted in BMI?

No! The muscle mass is not taken into account for calculating BMI

  • How Can I Reduce My BMI?

You can take several actions to reduce your BMI. You should ditch highly processed foods, increase fiber intake, and make use of protein, to reduce your BMI.

  • How Can I Help my Child Reduce his/her BMI?

You can help your child in reducing BMI by encouraging him/her to participate in physical activities daily. You can make them follow strict diets and take healthy meals.

  • BMI Reduction: How Long Will It Take?

You can reduce between 1-3% of your body fat per month. BMI reduction depends upon how seriously you take it and how much effort you are investing. Utilize the calorie calculator while eating food to measure calorie intake. By avoiding fatty foods and taking necessary actions you can observe a reduction in BMI.


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