Scale for measuring internal diameter of pipeline

The utility model discloses a scale for measuring an internal diameter of a pipeline. The scale comprises a telescopic section, and one, two or more circular standard extension rods with fixed length. The telescopic section comprises a circular case with a central circular hole, a circular scale, a spring and a bottom spring base. The front end of the circular scale is in clamp connection with a ball, and the rear end is provided with a top spring base. The front end of the case is provided with an outlet that matches with the circular scale. The circular scale and the top spring base are arranged inside the case, with the circular scale being beyond the outlet of the case. The front end of the bottom spring base is fixed at the rear end of the case. The spring is disposed in the case, with front and rear ends thereof abutting on the top spring base and the bottom spring base, respectively. All the standard extension rods are fixed together in order, wherein the front end of the front standard extension rod i