Is there an easy formula for maintenance levels with dieting? I thought that it was either 10 or 12 times your bodyweight, then add 1000 per day to gain.
Caloric requirements are way to individual for set formulas although a starting point must be established in which individuals can work from (subtract or add calories depending on their results). I have found 15x LBM to be an “easy” effective starting point for most individuals when combining macronutrients via the Massive Eating guidelines.
Of course, there are more scientific ways to do things...but you asked for an "easy" formula.
You really just have to experiment and find out for yourself.
I second the 15 cal./pound-lbm-as-a-starting-point recommendation. Works pretty well for most, but some tweaking is of course inevitable.