that sounds about right if your looking for the reasonably smallest room you can have.  It really depends on what your going to use the room for.  You might think about having some small rooms, and a few a little bigger.  That will give you some flexibility if  you change your mind about things later on.

to big of  a room isn't any good either.  You end up having to spend more time walking from one side of the room to the other.  

Figure out what your going to put in your room first.  then figure out how much space you need.  Just because a certain size space works for someone else, doesn't mean it will work for you.

I have run across as few really big rooms.  I admit that it could just be me.  The clinic I trained in had some real small rooms.  

As far ad meandering about I look at it this way.  If you have hot stones, or other equipment you need to make sure your all set up at the very beginning for the session.  Even then you may need extension cords or something else running along the floor which could pose trip hazards.

When looking for a room I know you sometimes also have to take what ever is available.  You don't always have the ability to choose.

We all do different things with our massage practice.  We all have different needs and issues to address.  Room size and what we do in it is just one of those things among many.