The first commercially successful calculator, the Arithmometer of Thomas de Colmar (1785-1870) was awarded a patent in 1820. His design for a mechanical calculator was based upon Leibniz's stepped drum mechanism. Throughout his life he worked to improved the mechanism for his machines.

This model has six entry settings, seven revolution counters and twelve windows to register the calculations. Two settings allow for Addition and Multiplication or Subtraction and Division. A contemporary review advertised that multiplications of eight figure sums by eight figure sums could be mechanically carried out in less than eighteen seconds. Thus eliminating the need for (expensive and time consuming) human computers.

With approximately only 60 machines surviving in private collections, the Arithmometer remains one of the rarest and most important artefacts from the age of digital mechanical computing.