Clavis Mathematicae

work by Oughtred

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June 24, 2026

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Clavis Mathematicae, meaning "The Key to Mathematics," was a significant mathematical work published in 1631 by William Oughtred. This manual, originally intended for a student, condensed a substantial amount of contemporary arithmetic and algebra into fewer than 100 pages. Oughtred's writing style was dense and favored excessive symbolism, making it challenging to read.1

Despite its difficulty, Clavis Mathematicae became a popular textbook in 17th-century England and was reprinted in both Latin and vernacular languages. The work introduced several mathematical symbols, two of which, "×" for multiplication and "::" for proportion, are still in common use today. The book influenced prominent figures such as Robert Boyle, Christopher Wren, and Isaac Newton.1

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William Oughtred
…famous under the title of Clavis Mathematicae (“The Key to Mathematics”), although it was not an easy text. It compressed much of contemporary European knowledge of arithmetic and algebra into less than 100 pages (in the first edition), while a somewhat obscure style and a penchant for excessive symbolism made…
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…famous under the title of Clavis Mathematicae (“The Key to Mathematics”), although it was not an easy text. It compressed much of contemporary European knowledge of arithmetic and algebra into less than 100 pages (in the first edition), while a somewhat obscure style and a penchant for excessive symbolism made…
Read More