Ronald Mack was born and educated in Warrnambool, and established his own accountancy firm there in 1930 after qualifying as an accountant in 1927 and working for Young and Outhwaite. In 1935 he married Helen Isobel Janet Lindsay. He was a Warrnambool city councillor in 1939-40. During World War II he served in the Australian Imperial Force, losing an eye at El Alamein. He returned to Warrnambool and resumed his accountancy practice, which in 1948 became Mack, Lohrey and Purcell.

Mack first entered the Victorian Parliament in 1950 as the member of the Legislative Assembly for Warrnambool, a seat he held until the 1952 election. In 1955 he was elected to the Legislative Council for Western Province, and this time retained the seat until his death. He was Minister of Health from 1961 to 1965, and in 1965 was elected President. He was President at the time of hid death at Hawthorn, and was given a State funeral. Mack was survived by his second wife, Winifred Helen Crutchfield, whom he had married in 1958, by one son and two stepdaughters of his first marriage, and by one stepdaughter and one stepson of his second marriage.