Toilets and bidets are usually placed beside each another because of their similar uses, but it is important that the two do not overlap because of problems with usable space. Just as a toilet should not be placed too close to a door or wall, a bidet should not be too close to the toilet bowl or cistern that it becomes difficult to use.
The Kohler space planning guide suggests a minimum distance of 16 inches between the center line of a toilet and the center line of a bidet in order to provide some “elbow room” for the user. The center line of a toilet or bidet is the imaginary line that cuts the toilet in two identical halves down the middle.
In addition to the elbow room distance, Nebraska's state building code requires a minimum distance of 20 inches between the center line of a bidet or toilet and “any bath fixture, wall or other obstacle.” Given that a toilet or bidet can be classified as a “bath fixture,” a minimum of 20 inches between a toilet and a bidet is recommended.
As can be seen from the variation in recommendations for Nebraska, the minimum distance between a toilet and bidet varies according to state law. Check local building codes and regulations before you begin work installing or moving a toilet and bidet in the bathroom.