I am am almost 13 years old, 4"7 and weigh 40 kg :"( How many calories do I need a day to loose weight? Like if I keep record of the stuff I eat and how many calories there are in it? Because I'm shorter than most people my age do I need to get less calories than them?

At 13 years of age and 4/7, weighing 40kg, you don't need to lose weight. Actually, your weight is fine.

At 13 years of age and 4/7, weighing 40kg, you don't need to lose weight. Actually, your weight is fine. I don't gain weight from my belly or legs but from my thigh area! Its really annoying and I want to lose that weight:(

Exercise is your best option. I would suggest running, which doesn't cost anything but good sneakers.
We come in all shapes and sizes, and how much we eat is only part of it. I've had chubby legs my whole life, no matter how thin or fat I was. I'm very short and try to joke that God meant for me to be taller but goofed.