I guess it depends on few other factors as well like, how long you have been on pills, your age and your overall health. Some women start ovulating again right away and find that they fall pregnant on their first pill free cycle. Others find that it takes a number of months for their natural menstrual cycle to resume. BC pills works by stopping ovulation. So once you are back to your normal cycle, you should most probably be able to conceive. However, if you had any ovulation problems before taking pills, these problems may still be there. So in any case, it would be advisable to consult your doctor while coming off with BC pills and starting TTC.
Before you start trying for a baby it's generally recommended that you wait until you have experienced one 'normal' menstrual period after stopping the pill. This will not only ensure that the hormones used by the pill to artificially control your cycle have left your system, but will also help your doctor to accurately pinpoint your due date when you do fall pregnant.
Charting your cycles right away after discontinuing the pill can help you to see when your own fertility returns and can help you see your own post-pill cycle characteristics.