John Douglas Cockcroft was born in Todmorden, West Riding of Yorkshire, England, on 27 May 1897, the eldest son of a mill owner, John Arthur Cockcroft, and his wife Annie Maude née Fielden. He had four younger brothers; Eric, Philip, Keith and Lionel. His early education was at the Church of England school in Walsden from 1901 to 1908, at Todmorden Elementary School from 1908 to 1909, and at Todmorden Secondary School from 1909 to 1914, where he played football and cricket. Among the girls at the school was his Future wife, Eunice Elizabeth Crabtree. In 1914, he won a County Major Scholarship, West Riding of Yorkshire, to the Victoria University of Manchester, where he studied mathematics.