How to Accurately Measure Your Toilet Rough-In Distance

Before installing a toilet, it is essential to determine the rough-in measurement. If you still have an existing toilet, here's how to measure the rough-in distance:

How to Measure Rough-In Distance with an Old Toilet

If the old toilet hasn’t been removed yet and you want to replace it with a new one, you need to measure the rough-in distance. In this case, you can measure from the center of the drain pipe to the wall. You might need to visit the neighbor upstairs, explain the situation, and measure the distance from the center point of the drain pipe to the wall to get the rough-in measurement you need. If there is a ceiling feature, you may need to remove part of the panel to take an accurate measurement.

Specifications for Toilet Rough-In Distances

1、The specifications for rough-in distances are generally standard. This distance refers to the distance from the center of the toilet drainage pipe to the wall. The main standards available in the market are typically 300 mm, 350 mm, 380 mm, and 400 mm, with 350 mm and 400 mm being the most common.

2、It is crucial to measure accurately beforehand. Toilets come in two types of drainage methods: wall-mounted (horizontal) and floor-mounted (vertical). The rough-in for horizontal toilets is generally 180 mm. Floor-mounted toilets have a more complex range of rough-ins, primarily 380 mm or 400 mm. Additionally, there is also a rough-in of 580 mm.

3、However, if your wall has been tiled, and you measure a distance of 400 mm, it might actually be 380 mm because manufacturers usually reserve an extra 20 mm to account for the thickness of the tiles.

4、If the measured distance after tiling is 370 mm, there’s no need to worry. This is because the toilet’s outlet diameter is typically 70 mm, while the diameter of the drainage pipe is generally 110 mm, leaving a 40 mm space to facilitate installation.

In summary：this article explains how to measure the toilet rough-in distance in the context of having an existing toilet. You can directly measure in the bathroom of your upstairs neighbor for more accurate results, but it’s important to discuss it with them beforehand.