What kind of calculating machine did Leonardo da Vinci design with numbered wheels?

Leonardo da Vinci designed a mechanical calculator using numbered wheels to perform arithmetic.

A drawing in the Codex Madrid I, dated to 1493, shows a system of geared wheels that could represent numerical operations. Each wheel's movement could be transferred to the next wheel, an arrangement related to carrying between digits. The design demonstrates that Leonardo understood how linked mechanical motion could encode numbers.

The machine was not a digital computer and was not powered by electricity. It was a proposed gear-driven calculating device, closer in principle to later mechanical calculators than to an abacus. Historians debate how completely the surviving sketch specifies a working calculator, so claims that Leonardo built a functioning example should be treated cautiously.

Mechanical calculators became practical much later. Blaise Pascal's Pascaline, introduced in the 17th century, is one of the earliest well-known manufactured calculators. Leonardo's drawing is significant because it shows an early Renaissance attempt to mechanize arithmetic.