Toilet Rough-In Calculator — Find Your Correct Measurement

The standard toilet rough-in in North America is 12 inches — measured from the finished wall behind the toilet to the center of the drain flange. About 80% of homes use this size. Less common are 10-inch rough-ins (found in older homes or small bathrooms) and 14-inch rough-ins (rare, mostly older construction). Measuring before you buy is critical because installing the wrong size requires expensive plumbing work.

Measure from the finished wall (not baseboard trim) to the center of the floor bolts (cap bolts) at the base of your toilet. If there are two sets of bolts, measure to the rear set. Remove the toilet for the most accurate measurement. Round to the nearest inch — if you measure 11.75″, your rough-in is 12 inches.

Yes, but it requires moving the drain pipe in the floor — a job that typically costs $250–$600 in labor if you open the floor, or more if it’s a concrete slab. A simpler option: if your rough-in is 10 or 14 inches, many toilet brands offer models specifically for those sizes. You can also use an offset toilet flange to shift the drain position by up to 2 inches without cutting the floor.

A toilet with too large a rough-in won’t reach the wall — leaving a gap behind the tank. A toilet with too small a rough-in physically won’t fit; the tank will hit the wall before the toilet seats properly on the flange. In both cases the wax ring seal won’t seat correctly, creating leak risk. Always verify your rough-in measurement before purchasing a toilet.