Cals studied Law at the Radboud University Nijmegen obtaining a Master of Laws degree and worked as a lawyer and prosecutor in Nijmegen from November 1940 until August 1948 and as researcher at his alma mater from February 1941 until May 1949. Cals also worked as a legal and economics teacher in Roermond from October 1943 until June 1945. Cals became a Member of the House of Representatives shortly after election of 1948 taking office on 19 August 1948 serving as a frontbencher and spokesperson for Education and Social Work. Following a cabinet reshuffle he was appointed as State Secretary for Education, Arts and Sciences in the Cabinet Drees–Van Schaik taking office on 15 March 1950. The Cabinet Drees–Van Schaik fell on 24 January 1951 and was replaced by Cabinet Drees I with Cals continuing his office. After the election of 1952 Cals was appointed as Minister of Education, Arts and Sciences in the Cabinet Drees II taking office on 2 September 1952. After the election of 1956 Cals retained his position in the Cabinet Drees III. The Cabinet Drees III fell on 11 December 1958 and was replaced by the caretaker Cabinet Beel II with Cals continuing his function. After the election of 1959 Cals once again retained his office in the Cabinet De Quay. After the election of 1963 Cals wasn't offered a cabinet post in the new cabinet and returned to the House of Representatives on 2 July 1963 serving as a frontbencher and spokesperson for the Interior and Kingdom Relations. Cals also became active in the public sector as a non-profit director and served on several state commissions and councils on behalf of the government.