Most of the 12" rough bowls will have somewhere between 2.5" and 2.0" behind the tank at 13.5"
Using a skirted TOTO bowl and 14" Unifit, you can bring it to .25" behind the tank. Those bowls only come with elongated.
From wall to closet flange screw it's 13.5" and from tile baseboard to screw it's 13". Should I go with 12" or 14" rough-in toilet? I already installed an Ultramax 12" and there is a 2" wall gap in the back. I want to purchase another Toto/toilet for another bathroom that is very small, and I can't have any wasted space. Solutions????
While there are slight differences item to item, the spec sheet shows 3/4" behind the toilet when using a standard rough-in. So, with 13.5", you'd still have about 1/4" to the wall, and the 14" unifit may be your best choice. You can fudge things slightly if you want more by maybe 1/4" or so since there's that much 'play' in the bolts to the flange.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014
Thanks for speedy reply. I opted for the 12" rough-in and was pleasantly surprised how well it looks with some space in the back. The Toto was sleeker and more compact looking than I thought it would be in such a small space. I left another blog reviewing my purchases 8/4/12. Thanks again.