I hear this question asked a lot. Weightloss comes down to calories in vs. calories out. The hard part is finding the exact number.
Enter the internet -- where there are websites for that kind of thing: http://www.nowloss.com/how-to-lose-weight-keep-it-off-permanently.htm
I love this website because it gives you a RANGE of what to eat for your activity level. I don't think it's realistic for anyone to keep themselves on a strict diet. I think if you're extra hungry one day, you should feel free to have a little bit more of a healthy option. Denying yourself nutrition when you need it is dangerous, and can lead to bingeing.
So type in your stats, and good luck on your continued efforts!!