How Much Value Does Adding a Room Bring to the Home?

[Devon Roberts]

I run into this problem a lot where I'm trying to find comps when running a CMA on a home but they all have a different number of rooms. I ask other real estate agents and they say the same old "it depends on the area." What does that even mean? Is there some sort of formula I could use or process where I can determine how much does an additional room brings to the value of a property? And vice versa?