Toilet rough in measuring: from wall to bolt cap. When talking toilets, the toilet rough in is the distance from the wall behind the toilet to the center of the outlet pipe where the waste leaves the toilet. The most common distance is 12 inches, so most toilets have a “12-inch rough.”. In some cases, the outlet is closer to or further away from the wall, especially in older homes. For those cases, toilets are available with a 10-inch rough or 14-inch rough. Before replacing a toilet, measure the rough in or make sure your plumber measures before buying. To measure accurately, measure from the wall–NOT the molding–to the bolt caps, as in this picture.