I think it depends on a lot of variables. The calories are an estimate based on what you have entered as part of your profile - height, current weight, age, etc. The calories also change based on how active you are. It also depends on the goals you have set and the level of difficulty your chose for yourself when you setup your profile.
I think you might want to monitor everything you eat and drink, and all your acitvities such as riding a bike, using an eliptical machine, playing tennis or golf, etc., inside the fitbit dashboard for a few weeks to determine if it is accurate for you. So all of those things factor in to it.
Welcome to the Fitbit community!
Hope this helps.
