A system for measuring diameter (inner and/or outer) of a tubular, the system in at least certain aspects including at least one linear distance measuring device with respect to which a tubular to be measured is movable, the at least one linear distance measuring device including a detector for detecting a surface of the tubular, the detector movably mounted to mount apparatus, the detector movable longitudinally along the surface of the tubular and movable axially in response to variation in diameter of the tubular, a rotatable head rotatable with respect to the tubular either outside of it or within it, the mount apparatus secured to the rotatable head, at least one signal production apparatus secured to the mount apparatus or head, and in communication with the linear distance measuring device, the at least one signal production apparatus for producing a signal indicative of distance between said detector and a known point, and transmitting apparatus for transmitting said signals to processing equipment for determining diameter of the tubular; and in certain aspects the linear distance measuring device is a laser device, electronic measurement device, acoustic measurement device, infrared measurement device, or linear variable differential transformer device.