How many calories do I need a day?

My goal is 100lbs and I'm 5 foot. I've felt myself start to relapse on my ED and it's been like that for a while again, but deep down I know I can ruin my health this way. What is a healthy number of calories to lose weight fast but not ruin my health? Thank you. Also I'm not too active, have a small/medium frame and am female, I'm also a teen.