Abstract: An apparatus for measuring an angle has a first planar bar member upon the edges of which are inscribed reciprocal angular scales corresponding to the tangent of an angle established by the position of the apparatus. A sliding measurement bar is maintained in substantially perpendicular relationship by an interlocking tongue and groove joint, and has an indicator for reading the set angle against the two planar scales. The tongue and groove joint and the two scales permit the apparatus to be constructed as a flat based planar device for both measuring an angle and transferring the measured angle from a physical object to a blue print or drawing of the object measured. Perpendicular spirit levels are placed in the sliding bar to allow the angle measuring device to be used with respect to horizontal or vertical positions for measuring the angle of actual physical construction such as beams or pipes.