12 inches is the standard toilet rough in size, and most toilets sold in the US fit that measurement. Some homes, especially older ones, may have 10 or 14 inch rough ins. If your rough in is 10 or 14 inches, you might be limited in your selection; we recommend the TOTO Carolina 1 Piece Toilet, which is available in both rough in sizes.
When talking toilets, the toilet rough in is the distance from the wall behind the toilet to the center of the outlet pipe where the waste leaves the toilet. The most common distance is 12 inches, so most toilets have a "12-inch rough." In some cases, the outlet is closer to or further away from the wall, especially in older homes.
The 215FC104.020 from the American Standard brand is equipped with a more traditional tank that fits a 12 rough. However, the bowl itself will fit a 14 inch. The reasoning behind this comes down to the nature of its design. This is actually a reasonably compact option that will ultimately help you save space and leg room in an undersized bathroom.
How to Measure for a 10 Inch or 12 Inch Rough in for a Toilet. Closet flanges have holes for bolts that secure the base of the toilet to the flange. 1 Determine a Toilet's Rough Opening. 2 Distance From the Toilet to the Wall Framing. 3 Install a Toilet in New Construction. 4 Typical Toilet Footprint Measurements.
A simple guide to measuring your toilet rough in, as explained by Josh, a Home Help Specialist at SUPPLY.com (formerly National Builder Supply). For more info on how to measure your toilet rough
So most toilets manufactured today are 12-inch rough-in toilets with a few models of 10-inch rough toilets and 14-inch rough-in toilets to cater to 10 or 14 inch situations which are still rare. If you have a toilet with 8 or 9-inch rough-in you have come across a very unfortunate and very very rare situation in the plumbing world.