Measure flange distance from wall without removing toilet
The important dimension is from the wall to the centerline of the bolts that hold the toilet in place. Measuring from the base is inaccurate. The tightest I have installed a toilet from the wall is 11 1/2" or so, when the toilet was 12" rough in. If you have baseboard that is 3/4" thick, you measurement could be as tight as 10 3/4" from the baseboard.