"What's the right weight for my height?" is one of the most common questions girls and guys have. It seems like a simple question. But, for teens, it's not always an easy one to answer. Why not? People have different body types, so there's no single number that's the right weight for everyone. Even among people who are the same height and age, some are more muscular or more developed than others. That's because not all teens have the same body type or develop at the same time.

It is possible to find out if you are in a healthy weight range for your height, though - it just takes a little effort. Read on to discover how this works. You'll also be able to put your measurements into our calculator and get an idea of how you are doing.

Not everyone grows and develops on the same schedule, but teens do go through a period of faster growth. During puberty, the body begins making hormones that spark physical changes like faster muscle growth (particularly in guys) and spurts in height and weight gain in both guys and girls. Once these changes start, they continue for several years. The average person can expect to grow as much as 10 inches (25 centimeters) during puberty before he or she reaches full adult height.

Most guys and girls gain weight more rapidly during this time as the amounts of muscle, fat, and bone in their bodies changes. All that new weight gain can be perfectly fine - as long as body fat, muscle, and bone are in the right proportion. Because some kids start developing as early as age 8 and some not until age 14 or so, it can be normal for two people who are the same height and age to have very different weights .

It can feel quite strange adjusting to suddenly feeling heavier or taller. So it's perfectly normal to feel self-conscious about weight during adolescence - a lot of people do.

Experts have developed a way to help figure out if a person is in the healthy weight range for his or her height. It's called the body mass index , or BMI. BMI is a formula that doctors use to estimate how much body fat a person has based on his or her weight and height.

The BMI formula uses height and weight measurements to calculate a BMI number. This number is then plotted on a chart, which tells a person whether he or she is underweight, average weight, at risk of becoming overweight, or overweight.

Figuring out the body mass index is a little more complicated for teens than it is for adults (that puberty thing again). BMI charts for teens use percentile lines to help individuals compare their BMIs to those of a very large group of people the same age and gender. There are different BMI charts for guys and girls under the age of 20.

A person's BMI number is plotted on the chart for their age and gender. Each BMI chart has eight percentile lines for 5th, 10th, 25th, 50th, 75th, 85th, 90th, and 95th percentiles. A teen whose BMI is at the 50th percentile is close to the average of the age group. A teen above the 95th percentile is considered overweight because 95% of the age group has a BMI less than he or she does. A teen below the 5th percentile is considered underweight because 95% of the age group has a higher BMI.

To figure out your BMI, use the tool below. Before you start, you'll need an accurate height and weight measurement. Bathroom scales and tape measures aren't always precise. So the best way to get accurate measurements is by being weighed and measured at your doctor's office or school.