What is the range of calories in a normal piece of lemon cheescake?

I know no-one can tell me the exact calorie count without knowing what exactly went in the cake. That is something even I don't know. Someone got it from a bakery and I really like it so I want to have a small piece a day from it (my brother will finish the rest, I'm sure). But I don't know about the ingredients so I can't coutn the calories. I know you can't tell me the exact calorie count , but maybe an approximate range? 

Well, it depends on the ingredients, size, and weight of the piece.. I would say anywhere between 250-450 calories!

All you can really do is guess.  Is this a baked cheesecake?

I make a triple chocolate divine cheesecake at Christmas time which I know is about 400 calories for a 1" wedge-slice.

If I was you, I would just hazard a guess, enjoy my piece of cheesecake exquisitely, and try to  make up for it at the gym!

Yeah, it is a baked cheesecake. But that is all I can tell. I counted it as 500 calories. Would a piece be more than that?

Could be. depends where you get it from. DId it feel buttery and creamy, or was it more jelly like? If it seems it may have been of sour cream (think about its consisitancy) then its on the higher scale. Plus the crust too - drier may be a few less cals (less butter).
I'd say guess it was 400, and go burn off some of that.