Oughtred was born at Eton and educated at the famous school there (where his father taught writing) and at Cambridge University. He was ordained a priest in 1603 and eventually became rector of Albury.

Despite his clerical post he found time to work on mathematics and he produced what was to become a very famous book on mathematics, the Clavis mathematicae (1631; The Key to Mathematics). This work dealt with arithmetic and algebra, and it is of historical importance because Oughtred managed to put into it more or less everything that was known at that time in those areas of mathematics. It rapidly became an influential and widely used textbook and held in high regard by mathematicians of the stature of Isaac Newton and John Wallis, himself a pupil of Oughtred. A number of mathematical symbols that are still used were first introduced by Oughtred. Among these were the sign ‘×’ for multiplication, and the ‘sin’ and ‘cos’ notation for trigonometrical functions. Oughtred also invented the earliest form of the slide rule in 1622 but only published this discovery in 1632. As a result, he became embroiled in a violent dispute with one of his former students, Richard Delamain, who had made the same invention independently.