What mechanical calculator did Leonardo da Vinci design using thirteen linked wheels?

Leonardo da Vinci designed a mechanical calculator using a series of linked wheels to perform arithmetic operations.

A drawing associated with Leonardo shows a calculating machine with thirteen geared wheels. The mechanism is commonly interpreted as an early adding device in which turning one wheel could advance another when a place value was carried. It demonstrates Leonardo’s understanding of geared transmission and numerical place value.

The design was not a programmable computer and was not documented as a commercially built calculator. The surviving drawing is also interpreted cautiously because some details are incomplete and later reconstructions necessarily make assumptions. Nevertheless, it is a significant example of Leonardo applying mechanical engineering to calculation.

The device is sometimes confused with Blaise Pascal’s Pascaline, which was built in the 17th century. Leonardo’s concept predates Pascal’s machine by more than a century, but it did not create a continuous line of documented calculator production.