Need calorie advise

I'm 27 at around 105lbs,  5 ft 3 and female on a 1200 cal diet with a sedentary job and I think I'm maintaining (this WAS my weightloss calorie number). I've never been over 117. I don't exercise now, but will soon. I calculated that if I start walking 2 miles in 30 minutes I'll burn about 100 cals. (Will do this until I join a gym) How much cals should I add to my diet each day for exercise? And when I'm not exercising? 1200, seems way too low for maintenance. 

I want to be able to eat more, exercise and maintain. What do I do???

Can anyone help?? I surely would appreciate it! :)

What I have read to maintain is to add 100 calories a day for a week to your total and see what happens. If you are still losing weight, add another 100 calories a day to the total for a week or so and so on. Keep doing this until you stay at your goal weight. Of course if you start gaining again, you will have to adjust accordingly. This is how I plan to do it when I reach my goal weight.  I think once you start exercising you will need even more calories. 

Hey there...there's no way that is your weight loss number.  But from reading this, i think your metabolism may have gone for a dive....are you gaining weight eating this much?

according to this site, if you are sedentary, your normal burn is 1500 calories, which would be maintenance.  The more you exercise the more you burn.  Like lcrum said -- add 100 cals at a time until you stop losing

To find how many calories you should eat to maintain multiply you weight in pounds by 11.  So your maintance calorie intake would be 1155 cal ories.  But we are told that it is unhealthy to eat less than 1200 a day.  If you exercise you can eat more calories offically but I find that exercising doesn't make any difference to me losing weight it's mainly diet.  I am running a marathon in 4 weeks and until I started dieting 4 weeks ago i hadn't lost a gram even though I run 6 days a week.  Reducing my maintance calorie intake by 500 a day and I am slowly losing weight.  Don't let exercise be an excuse to eat anything!