What early machine did Leonardo da Vinci sketch to perform arithmetic calculations?

Leonardo da Vinci sketched a mechanical calculator intended to perform arithmetic calculations.

The device appears in Leonardo’s papers from the late fifteenth century and used a series of geared wheels. Turning one wheel could advance another by a controlled amount, creating a mechanism suitable for adding numbers. The design is sometimes called Leonardo’s calculator or an adding machine.

Leonardo did not leave evidence that he completed or used a functioning calculator. Modern reconstructions have been built from his drawings, although scholars debate how fully the surviving sketches specify the intended mechanism.

This design belongs to the long history of mechanical calculation, which later included Pascal’s Pascaline in the seventeenth century. It is different from Leonardo’s mechanical lion and other automata, whose main purpose was movement or display rather than arithmetic.