Abstract: An optical gauging apparatus is provided for determining the deviation of a pipe end from squareness with respect to the pipe axis. A viewing scope is placed centrally in the pipe end to be measured so as to be directed at right angles thereto, and a graduated target is centrally located in the opposite end of the pipe. Sighting through the scope, the distance R of the intersection of the line of sight from the center of the target is determined. The deviation S from squareness may then be calculated from R, D the diameter of the pipe, and L the distance of the target from the end being measured, by the equation: S=RD/L.