Okay, everyone's body is different. You cannot give one number (for caloric intake) and expect it to work for everyone.
Think of it like an equation of caloric income versus expenses. When it's balanced, the answer will stay the same. If not, that answer will either grow or shrink.
If you want to know the details, I would calculate your Basal Metabolic Rate (BMR). This is the amount fo calories your body burns in order to keep itself alive (i.e. if you did nothing the entire day, you body would burn this amount). This changes with your body weight and body composition of course.
"Dieting" involves eating just under this amount by 100-200 calories (my BMR last I checked was 2200 calories; I weigh about 205-ish pounds). FOr me to lose weight without exercising, I would eat about 2000 calories a day. This strategy loses you probably 1 or 2 pounds a week. That's as quick as your body can change really; the rest of weight change tends to be water weight, food, clothing, and even time of day you weigh yourself. Changing your body takes time, period.
If you start exercising, this number increases. Exercising a moderate amount, my metabolic rate goes up to about 3000 calories a day. This has multiple advantages. It helps clear your veins of excess cholesterol (particularly the bad kind), keeps blood pressure at healthier levels, improves sleeping patterns, can change body proportions (rather than just shrink them evenly). The last one is due to the fact that exercise tends to build muscle on top of burning fat. Even running or cycling builds muscles in the legs, particularly anaerobic intervals.
Also, you cannot target fat loss (someone's mentioned this). Your body is programmed to burn fat off of your body in a particular pattern (in fact, there are generalized patterns here between men and women). This, you cannot change. However, you CAN target muscle gains and toning. Toning encourages body areas to become smaller and tighter, giving you a sleeker look than you had before.
ON Queer as Folk (the UK version), the characters state 30 lbs gets you about an inch. There most definitely is going to be large amounts of variance, whatever the actual average is. Just remember, fat loss and toning is going to help you achieve what you want.
I hope this helps!