Before you buy a replacement toilet, check its rough-in. This is the distance from the finished wall behind the toilet to the centre of the floor drain, as American Standard describes in its product specifications. A toilet made for a different rough-in may not fit your bathroom, even if the bowl looks about the same size.
Measure from the wall, not the baseboard
With the existing toilet still in place, measure from the finished wall to the centre of one of the bolts holding the toilet to the floor. Those bolts usually line up with the centre of the drain flange. Keep the tape straight and measure perpendicular to the wall.
Do not measure from the front of the baseboard. Do not add the thickness of drywall or tile when your starting point is already the finished wall. If a thick baseboard makes it hard to place the tape at the wall, account only for that obstruction or ask for help confirming the measurement.
Twelve inches is common, but toilets are also sold for other rough-in dimensions. Record the measurement instead of assuming it is standard.
Check the rest of the space
The rough-in is only one fit question. Note the distance to a side wall or vanity, the space in front of the bowl, and whether the bathroom door clears it. If you want an elongated bowl, check its overall projection. Photograph the existing toilet and the room from a few angles before shopping.
When to get a second opinion
If the bolts are hidden, the toilet sits at an angle, the measurement falls between common sizes, or you are planning a larger bathroom change, have the fit checked before ordering. Our toilet service team can discuss replacement options and the work involved.