Born in New Haven, Connecticut, in 1938, the middle child of Alfred and Margaret Carrington, Grant Carrington grew up in the suburban town of North Haven, graduating from North Haven High in 1956, getting bachelors and masters degrees in math from NYU and the University of Florida. He worked as a computer programmer for Goddard Space Flight Center, the University of Florida, the Naval Telecommunications Command, Savannah River Ecology Lab, Westinghouse Corporation, and the Treasury Department of the United States, from which he retired in 2004.