The others are right, we need to know your current weight to give you a ballpark idea. Someone who weighs 350 lbs could likely lose weight on 2500 cals/day, but someone who weighs 150 lbs would likely gain on the same amount. The heavier we are, the harder our bodies have to work to maintain eqilibrium, thus the more calories we burn just "sitting around" or doing normal daily tasks than someone who isn't carrying extra weight.
The 1200 calorie "rule" is a guideline the medical community generally recommends as the MINIMUM amount any woman should consume. Less than that, you run the risk of malnutrition if not under medical supervision. Of course there may be some exceptions (very petite women, elderly people) who might be able to safely consume less than 1200 and stay healthy...but generally speaking, most people would agree that you shouldn't eat under 1200 for any length of time.
With that said, I caution you against saying, "1200 is safe, OK! 1200 it is!" Depending on your current weight and your current calorie consumption, this may be WAY too low for you right now. If it's not sustainable, you won't stick with it--and you will likely not keep the weight off even if you do lose. (Been there, done that!) The other important thing to consider is, as you go along, you will not be able to adjust your calories down because you are already at the minimum. This can make plateaus impossibly frustrating.
If you don't want to reveal your weight here, there are many online tools that can help you. Google "calorie calculator" and you'll get a bunch of results. Punch in your current weight, height, etc. and it will give you an idea of how many calories you need to maintain your curent weight. They may not all say the exact same thing, but it will give you an idea. Generally speaking, a good place to start is to cut 500 calories off your "maintenance" calories to lose 1 lb/week. (3500 calories equals one pound of fat, so a 500 calorie deficit/day = 3500 cals at the end of 7 days.) So, for example, if you need 2500 calories to maintain, try a 2000 calorie limit for a few weeks to start. You can always adjust up or down from there. Our bodies are all different--someone with identical weight/height/activity "stats" as you may have different results with the same calorie intake. Think of it as an experiment
Also remember that even though, in theory, you should lose 1 lb/week with a 500 cal/day deficit, it doesn't always work so nicely in real life. You may lose 3 lbs one week, 1/2 lb the next week, 1 lb the following week, nothing the next week and maybe even a gain the week after that. Our bodies DO fluctuate, especially us women with our water retention/montly cycles, etc. Don't get discouraged as this is NOT a linear process for most of us!
Hope that helps and good luck on your journey!!
