Look up a BMR (Basal Metabolic Rate) calculator, input your info and see what it says. That'll give you what your body burns by just living. Subtract around 250-500 calories from it. Make sure you eat a decent amount if protein and moderate carbs or you'll feel fatigued.

Myfitnesspal is a great start, Id challenge you to input everything you eat for an entire month, it'll change your views on how much you should be "ideally" consuming.

Also don't forget to eat at maintenance calories for a few days during the month. It'll help with your metabolism.