1200cals a day is the bare minimum your body requires and will acheive weight loss. Anything under that, and your body will head towards starvation mode... not good for weightloss.

I'm currently doing 1200 cals a day following a program. I'd suggest using calorie king and inputting your details and I think it works a calorie limit out for you based on those..... but the limits are pretty high.

Perhaps start with 1800 and see how you go. If you're coping fine but want to see a few more results (and you are training aswell), perhaps push it down 100 cals at a time. Or you could start at 1500 or even at the 1200 and see how you handle it with the option of adding cals if you feel it's not enough.

I've adapted perfectly fine to 1200 cals and I was well into the morbidly obese category. Drink lots of water... water is amazing.
Good luck!!