19 years old - confused about calorie goals

at 19 years old, should i be following the rules prescribed for kids/teens or adults when it comes to determining calorie needs?

my stats, in case it helps: female, ~5'7", ~120lbs, sedentary

well you have a bmi of only 18.8, which is bordering underweight so i hope you're not trying to lose any weight. you are also NOT SEDENTARY unless you stay in bed all day, don't walk to the store, school, or anywhere. you are likely lightly active if you don't do any structured exercise. that being said, you burn about 1860 calories a day according to phord.com/cc and you should NEVER consume less than 1500 being a growing teen and all. 

FYI, even at sedentary you'd burn 1620 but most people are not sedentary since they aren't handicapped or physically incapable of moving.

nope, i'm just trying to maintain my current weight. i thought 'sedentary' seemed appropriate because i drive to work, sit for 8.5 hours typing all day, and do nothing in the evenings. (bad, i know!) however when i start school i'll at least be walking around to classes and such, so i think 'lightly active' fits.

i was thinking that 1900 was a good target so i wasn't too far off.

thanks!

with a teensy bit of walking here and there, some AM pushups, crunches, etc. you can definitely eat 1900 for maintenance. you might want to consider weight lifting to build some muscle, it will cause a bit of gain but you can stand to gain a few pounds anyhow.