Johann Zacharias Dase

The German mental calculator who computed pi to 200 decimal places — in his head, over two months.

A 100-digit multiplication problem, solved entirely mentally in eight hours and 45 minutes, established Johann Zacharias Dase as a premier mental calculator of the nineteenth century. Born in Hamburg on June 23, 1824, he demonstrated an atypical arithmetic capacity that functioned independently of formal education, relying instead on intuitive skills he attributed to childhood games of dominoes.

Mental Calculation Feats

Dase traveled across Germany, Austria, and England at age 15 to demonstrate his numerical abilities. He performed high-speed mental arithmetic, such as multiplying two 20-digit numbers in six minutes or two 40-digit numbers in 40 minutes. Despite these results, Carl Friedrich Gauss noted that a person skilled in calculation could complete similar tasks using pencil and paper in approximately half the time Dase required.

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Mathematical Contributions

In 1844, Dase calculated pi to 200 decimal places over two months using a Machin-like formula. His work included the creation of Tafel der natürlichen Logarithmen der Zahlen and the extension of integer factorizations from 6,000,000 to 9,000,000. While his output was prolific, he lacked formal training in mathematical theory, and attempts by Julius Petersen to instruct him in Euclidean theorems failed.

Professional Life and Health

Dase struggled to find consistent employment, taking a position in the Railway Department of Vienna in 1844 before moving to Mannheim and Berlin. Throughout his life, he managed epilepsy. Carl Friedrich Gauss attempted to secure him a full-time role at the Hamburg Academy of Sciences to focus on his computations, but Dase died in his hometown of Hamburg on September 11, 1861, before this could occur.