Bachelor of Science, Queen's University, Belfast, Ireland, 1931. Research student, St. John's College, Cambridge University, England, 1933.
He worked at King's College in London, where he met Olga Taussky, a matrix and number theorist. He worked for the British Admiralty during World War II. In 1945 the Todds emigrated to the United States and worked for the National Bureau of Standards. In 1957 they joined the faculty of California Institute of Technology in Pasadena, California.
John Todd retired from the faculty, and in May, 2001 was honored by a symposium at Caltech in honor of his 90th birthday. He died at his home in Pasadena, California on June 21, 2007.
Member American Mathematics Society, Society Industrial and Applied Mathematics, Mathematics Association American (governor 1980-1983).
Married Olga Taussky, September 29, 1938 (deceased 1995).