I posted this link a little while ago. Almost nobody looked at it even though people always ask questions like this.
Resting Metabolic Rate Calculator
Check out the link. If you know your body fat % this will be fairly accurate for giving you a basic idea of how many calories you burn in a day(without your lifting, activity etc) ---its a resting metabolic rate. Having the body fat % makes it much more accurate than any formula that only requires weight/height etc(considering that a pound of fat only burns about 3 calories a day or something crazy like that). But Uriel is right...you do need to experiment on your own, this wont solve all of your problems but it is a good base.
Good luck, let me know if you have any questions. :)