When shopping for a new toilet, one measurement matters more than most homeowners realize: the rough-in size. If you don’t get this right, the toilet you buy might not fit your bathroom—or could leave an awkward gap from the wall.
In this guide, we’ll explain what a rough-in is, the different sizes available, how to measure it correctly, and why building code matters. Whether you’re replacing an old toilet or doing a full remodel, knowing your rough-in will save you time, money, and frustration.
The rough-in is the distance from the finished wall behind your toilet to the center of the toilet flange—the pipe that connects your toilet to the drain.
This measurement determines how far your toilet will sit from the wall and whether it will align with your plumbing correctly. If the rough-in size doesn’t match, the toilet may not fit—or you may need to use an offset flange, which can complicate the installation and potentially affect flushing performance.
How to measure your rough-in:
Toilets typically come in three rough-in sizes: 10-inch, 12-inch, and 14-inch. Here’s what to know about each.
This is the standard size found in most modern homes.
12-inch toilets are:
Common in older homes or bathrooms with tight layouts.
10-inch toilets:
Occasionally found in custom-built or pre-1960s homes.
Toilets made for 14-inch rough-ins:
Installing a toilet with the wrong rough-in can lead to poor alignment, performance issues, or cosmetic problems like visible gaps behind the tank.
In older homes built before standardized codes, rough-in sizes often varied. Builders worked around framing and plumbing, which sometimes meant toilets were set at 10 or 14 inches instead of a consistent measurement.
Today, most homes are built to accept a 12-inch toilet. This size balances installation ease, effective flushing, and space efficiency. Manufacturers have followed suit, making most toilets with a 12-inch rough-in by default.
Beyond the rough-in measurement, building code also dictates how much space you need on either side of the toilet.
According to the International Residential Code (IRC):
Ignoring these requirements could make your bathroom feel cramped—or lead to failed inspections during remodeling.
It depends on your setup, but generally, it’s not ideal.
Some manufacturers offer adjustable toilets or special mounting brackets to handle multiple rough-in sizes, but these are less common and typically more expensive.
At The Toilet Guy, we always measure before we recommend.
We’ve seen it too many times: a new toilet arrives, only to find it doesn’t fit, sits crooked, or won’t flush right. A simple 30-second measurement can prevent hours of hassle.
When we measure, we also consider:
When we install a toilet, it fits like it should—flush to the wall, properly aligned, and fully code-compliant.
Rough-in size might seem like a small detail, but it can make a big difference in how smoothly your installation goes.
Before buying a toilet online or from a home improvement store, take the time to measure from your finished wall to the center of the toilet bolts. If it’s not exactly 12 inches, don’t worry—there are still solid options for 10-inch and 14-inch installations.
And if you’re unsure or just want to make sure it’s done right?
Give The Toilet Guy a call. We’ll come out, take the measurement, and install the right toilet for your space—no guesswork, no surprises.
Every installation is backed by our 90-day labor warranty, and we only use high-quality components like solid brass bolts and stainless steel supply lines.
Need help finding the right toilet for your bathroom?
Contact us today—we’ll make the process simple, honest, and stress-free.
