Puberty follows a unique timeline for each individual child. From the time it starts, kids may grow as much as 10 inches and gain muscle, fat, and bone as their bodies develop to adult form. These changes may happen suddenly and involve rapid weight gain, which may lead to feelings of self-consciousness as children adjust to their new bodies. Some may enter puberty as early as age 8. Others may not begin until they reach their early teens. As a result, there’s a wide range of “normal” weights, shapes, and sizes.

The weight range for 13-year-old boys is between 75 and 145 pounds. Weights in the 50th percentile for this age land at 100 pounds. If a child falls into the 50th percentile for weight, this means that of 100 kids his age, 50 will weigh more while another 50 will weigh less. If a child falls in the 25th percentile for weight, 75 out of 100 kids will weigh more and 25 will weigh less.

Weight percentiles for 13-year-old boys:

5th percentile75 pounds
10th percentile80 pounds
25th percentile88 pounds
50th percentile100 pounds
75th percentile116 pounds
90th percentile133 pounds
95th percentile145 pounds

The weight range for 13-year-old girls is between 76 and 148 pounds. Weights in the 50th percentile for this age land at 101 pounds. A weight in the 50th percentile means that of 100 13-year-old girls, 50 will weigh more while 50 will weigh less, and so on.

Weight percentiles for 13-year-old girls:

5th percentile76 pounds
10th percentile80 pounds
25th percentile89 pounds
50th percentile101 pounds
75th percentile116 pounds
90th percentile135 pounds
95th percentile148 pounds

The true average weight of 13-year-olds is trickier to pin down. That’s because a number of things can influence body weight for young teens.

Rate of development

Children enter puberty sometime between 8 and 14 years old. If you take a sample of 13-year-old kids from the same room, you’ll see a wide range in body sizes and weights. Some kids may have finished the process while others are just beginning to go through the many changes that lead to physical maturation.

Height and body makeup

Your child’s height may also influence their weight. Taller kids may weigh more than shorter ones, but that’s not always the case. Bone density and muscle mass are two other important factors. There are many variations in body composition. Since muscle weighs more than fat, for example, a child who is more muscular may weigh more than a child who is leaner or one who has more fat in place of muscle.

Genetics

While diet and activity levels play a role, body shape and composition are also influenced by the genes children inherit from their parents. In other words, people from different genetic backgrounds often have different fat distributions or body compositions that may inherently influence body shape, size, and weight.

Location

Even where a child lives may influence their body size, height, and weight. This has to do with a number of things, including access to food, socioeconomic level, cultural practices, genetics, and other factors, like the onset of puberty, which can vary by geographic location around the globe.

Body mass index (BMI) takes into account more than simple averages with regard to weight. It is a standard for calculating body fat percentage using height and weight without skinfold measurements or other more direct methods, like water weighing. With teens, BMI calculations also factor in age and sex, what’s referred to as “BMI-for-age.” This figure shows where your teen lands on the spectrum of other kids the same age.

To calculate your child’s BMI, use this calculator provided by the Centers for Disease Control and Prevention. You’ll enter your child’s age, sex, height, and weight, from which you’ll get a result indicating if your child is underweight, healthy weight, overweight, or obese.

Less than 5th percentileunderweight
5th percentile to 85th percentilehealthy weight
85th percentile to 95th percentileoverweight
95th percentile and greaterobese

Why is this information important?

Kids who fall into the overweight and obese categories may be at a higher risk of developing type 2 diabetes, high cholesterol, or other weight-related health issues. That said, BMI is not always the most accurate measure, since it doesn’t take into account muscle mass or other factors that might affect weight, specifically muscle versus fat.

Your teen may have a number of questions about their changing body during puberty. Maintaining an open line of communication may help foster a positive body image and body confidence.

Educate your child on how puberty works

Explain that it’s part of normal development and that weight gain is part of the many changes they’ll encounter along the way.

Talk about positive self-image

Bodies come in all different shapes and sizes. It may be helpful to ask your child what they like about themselves. You can get in on this, too, and be sure to share characteristics beyond the physical. Steer language to the positive with bodies and body image. Words like “fat” or “skinny” or hurtful nicknames may distract from the issue at hand.

Discuss the messages from media

Talk about what your child sees on television, in movies, and online, such as music videos and social media. It may seem at times like there’s an “ideal” body type that’s shared, but encourage your teen to look beyond or even question these images.

Monitor your child’s internet habits

Some rules around device usage may help diffuse the negative messages around body image.

Help your teen develop healthy eating and exercise habits

Small changes can help with weight, include skipping sugary beverages or taking a short walk around the neighborhood.

Puberty is a time of physical change and emotional challenges. Averages and percentiles are important to consider, especially regarding the potential for obesity-related health issues that can arise in the teen years. That said, focusing on your child’s body image and self-talk is equally important work. If you have concerns about your child’s weight, development, or potential self-esteem issues, consider making an appointment to speak to a pediatrician.