Abstract: A multi-functional tape measure is provided with a top-mounted viewing window which reads a bottom surface of a coiled measuring tape for providing interior distance measurements using measuring indicia disposed on the bottom surface of the tape. The bottomside measuring indicia has an applied correction factor to compensate for the size of the housing and provide the dimension needed. The tape measure is also provided with a level for indication of a surface that is level and plumb. Further, the tape measure is provided with a fold-out locking T-square mechanism.