How to measure rough-in
Rough-in is the distance from the finished wall behind the toilet to the center of the two closet bolts (the bolts holding the bowl to the floor flange), not to the flange itself, and not from the baseboard. Measure along the floor, not the wall. Most US residential toilets are built for a 12″ rough-in. 10″ and 14″ exist for tight bathrooms or older construction, but they cost more and come in far fewer styles, so confirm your actual measurement before assuming you need one.
One-piece vs. two-piece
A two-piece toilet ships as a separate tank and bowl, bolted together on site. It’s the more common, generally less expensive option, and individual parts (just the tank, just the bowl) can sometimes be replaced without swapping the whole fixture. A one-piece toilet is a single fused unit: fewer seams means fewer places to leak or trap grime, and a lower profile, but the whole unit gets replaced if either half fails.
Round vs. elongated bowls
Elongated bowls are about 2″ longer front-to-back than round bowls. That extra length is generally considered more comfortable and is the ADA-referenced shape for accessible installs, but it needs more clearance in front of the bowl, so check your local code’s minimum clearance before committing in a tight powder room. Round bowls are the space-saving option for small half-baths.
Flush rating and trapway
MaP (Maximum Performance) scores tell you how many grams of waste a toilet clears in one flush during independent lab testing. Higher is better, and most modern residential toilets score well above what a household actually needs. A fully glazed trapway (the S-curve inside the base) resists buildup better than a rough cast one, which matters more for long-term cleaning than day-to-day flush power.