Just set up a food tracker for your account, then key in the word "coffee", and the data base will bring up several answers for that word. Pick the one that seems closest to your actual cup of coffee.
Coffee is a great example of why focusing on calories seldom gets you where you want to go. Coffee is a stimulant, and stimulants help you lose weight no matter how many calories they contain. But they also speed you up, so it's not a recommended way to lose weight, but you see the issue here -- it's metabolism, not calories. Calories aren't unimportant, but how quickly and how well you digest and metabolize the food you eat is the more important issue for long-term dietary changes.