Roughing it - 12" or 12.5"?

When a toilet is specified as a 12" rough in - does that mean 12" from the unfinished framing to the center of the closet flange or is it measured from the expected finished wall (i.e. 1/2" or 5/8" further out)?

The reason I ask is I frequently see a gap behind toilets of about 3/4" to 1". I realize you need a tolerance in there, but a 1" gap seems excessive.
Thanks for your input!

The dimension is from the FINISHED wall, so if you are using 1/2" drywall, you'd want 12.5" from the studs. Some people go out a little further since you never know if they decide to put tile or wainscoating up and make the wall functionally thicker.

There is no standard on gap between the toilet and the wall...just that it will fit if you have 12". Some can run from nearly touching to over an inch. SOme of this is to account for manufacturing tolerances.

Manufacturers are building in more tolerance then before.

I used to cut them at 13" from the rough wall to give me 12-1/2" in case they ran tile or wainscoating.

But now, 12" to finish is plenty with the new bowls.
With some, you could even pull it back some.

toilet

A 12" toilet on a 12" rough could give anywhere from 1/8' to 1" behind the tank depending on how much leeway the manufacturer builds into his design. There is no standard, but as Terry said, we usually rough them at about 13" to accomodate most possibilities of wall finish. A 3/4" thick tile on a mud base can mess up a tight 12" rough opening in a hurry.