What is the average weight of a 162 cm girl?

That would be someone about five feet five inches tall. You say girl, but give no more precise a description.

Therefore, i used a body mass index calculator and put in a height of 5' 5", a weight of 110 lbs (50 kilograms) and an age of 15 years. It determined that that weight is in the lower 25th percentile, which means that three out of four girls 15 years of age who are 5' 5" tall weigh more than that. It recommended an ideal weight of 122 lbs. for a 15 year old girl, slightly more than 55 kilograms.

Here is a site where you can plug in your height and find out what a healthy range of weight would be for that height.

http://www.nhlbisupport.com/bmi/bmi-m.htm

It is not that simple and answer as it is dependent on one's frame size -small, medium or large bone structure. Also it depends on BMI (Body Mass Index) and/or relative athletic conditioning, as muscle weighs more than fat. Athletes have less fat and, as such, have a different weight chart criteria.

Sorry if this makes matters a bit more complicated.

A simple answer for a 162 cm (5 ft 5-1/2 in), 15 yr old girl, medium build is a range of between 50 Kg(110 lbs) and 62Kg (135 lbs).

I see that by the BMI charts for a medium-framed young lady, optimal weight might be closer to 50-53 kg. However, weighing more than that is still considered healthy, too.