average age of a 12-year-old

What is the average weight for a 12-year-old?

When children hit adolescence, they begin to look out for certain body changes such as height, looks, and weight. They are mostly concerned about their image and so they try very hard to look after their bodies. There is no specific age weight for 12-year old’s which is considered normal. There are many factors beyond the usual biological sex that influence the weight of a person at this age. 

Their height, body composition, environmental factors, and underlying health issues all play a key role in determining the weight of a person. As you read on, you will get to know the average weight of both girls and boys at this age, and how the factors mentioned above determine the weight of a person.

How can you assess a healthy weight?

Healthy weight guidelines are based on body mass index or BMI (a number used to determine the weight of a girl or boy). The United States Centers for Disease Control and Prevention has established a range of weights that are classified as normal. This range also takes into account the differences in how children grow.

What is the average weight of a 12-year-old girl?

According to the Centers for Disease Control and Prevention charts, the average weight of a 12-year-old girl is 92 pounds or 42 kilograms. The weight of girls at this age varies though. 

This is because girls enter puberty at different ages and girls who started the puberty process early at this stage can weigh more than girls who have not. 

A study published in 2013 in “Pediatric Obesity” reports that having a higher BMI early in life can cause early puberty. For example, girls between the ages of 6 and 12, tend to gain between 4 and 7 pounds per year before puberty starts. 

So, a 12-year-old girl who only gains 4 pounds a year will weigh less than a girl of the same age who gains 7 pounds per year. Both these groups of girls are however considered to have healthy weights. 

Here is the average range of weight by percentile for girls

PercentilePounds (lb.)Kilograms (Kg)

What is the average weight of a 12-year-old boy?

The average weight of a 12-year-old boy is 89 pounds or 40 kilograms according to the Centers for Disease Control and Prevention. Like girls, boys can differ in weight at this stage. 

Certain factors like 

  • genetics 
  • height 
  • start of puberty and 
  • body composition can bring about variations in weight.

Below is the average range of weights by percentile

PercentilePounds (lb.)Kilograms (Kg)
The average weight of 12-year old girls by percentile

What are the factors that bring about differences in weight and BMI?

There are a lot of factors that can influence the weight of a 12-year-old. Here are some of a few factors to consider in order to determine whether your adolescent child has a healthy weight or not.


A shorter person generally weighs less than someone who is tall. BMI calculators take into account the height of adolescent children. Two children who are of the same weight but of different heights (for example, a height difference of 6 inches) will have different BMIs. 

The taller of the two children will fall within the healthy weight range whereas the shorter one may be overweight.


Genetics is also another factor that influences the weight of a 12-year-old. The genetic makeup of some people makes them more prone to obesity. The genes the children inherited from their parents can also predetermine their weight irrespective of their diet and exercise habits.

Body composition

A person’s body composition should be taken into account when assessing weight. A child with a higher-than-average amount of body fat may weigh more than the average. A child with significant muscle tone can weigh more than that of a child with more body fat. This is because muscle has a higher density than fat.


The location or environment of the child may also affect the weight and overall body size of the child. Puberty begins at different ages across the world. For example, on average, puberty begins earlier in northern Europe than in southern Europe. 

Socioeconomic factors and access to food in other parts of the world can affect weight. The culture or cultural practices of the child’s location also play a role in weight variation.

Sickness or ailments

Some health conditions can lead to weight gain and weight loss in children leading to variations in weight amongst 12-year-old children.

Examples of health conditions that can cause weight gain include:

  • Depression 
  • Cushing’s disease 
  • Hypothyroidism 
  • Polycystic ovary syndrome (also referred to as PCOS), etc.

Here are some examples of health conditions that can lead to weight loss in children

Eating disorders, diabetes, peptic ulcer, hypercalcemia, depression, ulcerative colitis, Addison’s disease, etc.

What can you do to help a 12-year-old who feels insecure about his or her weight?

Here are some of the things you can do to help ease the mind and concerns of your 12-year-old.

Let the child know that people differ in weight, size and stature

Help the child create a positive body image by making him or her understand that everyone is beautiful in his or her own way. There is no specific standard for beauty and so he or she should not feel insecure about his or her weight.

Address what the child sees on the internet

Movies, images, social media all contribute to peer pressure and promote a certain body type that people find ideal. Make sure to address this issue and you can help your child move past his or her weight concerns.

Have a talk with your child about body weight and image

When a child hits puberty, it can become too much for them to handle. Their bodies and hormones keep on changing within a short period of time. They can therefore develop new feelings and insecurities and so it is helpful to have a talk with them to explain what puberty is and what it means with regard to the changes they will experience.

Key Takeaway from this Article

The average weight of a 12-year-old boy is about 89 pounds or 40kg, while the average weight for a 12-year-old girl is 92pounds or 42kg. However, these values are only averages and a lot of people may have weights differing from the average.

Some of the factors that may influence the weight of a 12-year-old include their height, body composition, environment and underlying medical conditions.


Michael Sarfo
Content Creator at Wapomu

Michael Sarfo is a graduate of the University of Ghana, Legon. He is a content creator for enochkabange.com and a writer for Wapomu

Dr. Ehoneah Obed is a registered pharmacist and a member of the Pharmaceutical Society of Ghana. He has a Doctor of Pharmacy degree from Kwame Nkrumah University of Science and Technology and has experience working in a Tertiary hospital as well as various community pharmacies. He is also a software engineer interested in healthcare technologies.

His love for helping others motivates him to create content on an array of topics mostly relating to the health of people and also software engineering content.

He is knowledgeable in digital marketing, content marketing, and a host of other skills that make him versatile enough to uplift any team he joins.

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