Which inventor developed the first widely used mechanical calculator, the arithmometer, in 1820?

Charles Xavier Thomas de Colmar developed the first widely used mechanical calculator, the arithmometer, in 1820.

The arithmometer was a mechanical calculating machine capable of addition, subtraction, multiplication, and division. Thomas de Colmar patented his design in France in 1820 and continued improving it over many years. Later versions were manufactured and sold for business, government, and scientific work.

Earlier machines included Blaise Pascal’s Pascaline and Gottfried Wilhelm Leibniz’s stepped reckoner. Those inventions were important but had limited production and use. The arithmometer became the first mechanical calculator manufactured and sold in substantial numbers, making it a landmark in office automation.

It was not a programmable computer. Operators entered numbers by setting controls and turned a handle to perform calculations. Charles Babbage later pursued far more complex calculating engines, but his major engines were not completed as commercial products during his lifetime.