Calories in Chicken Breast???

How many calories is in a Large Chicken Breast? I eat it alot, and have no idea how many calories is in it ,  and would like to track it accurately haha! I'm trying to make sure I eat enough calories per day (around 2,000) to maintain.. Also, 4 oz of chicken breast looks like a deck of cards right? Well the size of the chicken breasts I'm referring to is the size of about 4-5 deck of cards... and on the bag, it says 120 per 4 oz..so this chicken breast would be about 480/600 calories right? (120x4)

260 for a large chicken breast according to my dietitian :D

It may sound like overkill, but I keep a scale in my kitchen both for recipes and to answer exactly this sort of question.

A large chicken breast can be anywehere between 200 - 280 :)
Use this; http://caloriecount.about.com/calories-chicke n-breast-meat-only-i5064?size_grams=140.0