What type of machine did Leonardo da Vinci design to perform addition and subtraction with numbered wheels?

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

Leonardo’s notes include a drawing of a calculating machine made from a series of geared wheels. Turning one wheel would transmit movement to another, allowing the device to represent place values in a decimal system. The design is commonly described as capable of addition and subtraction, although the surviving sketch does not provide a complete operating manual.

The machine is important as an early concept for mechanical calculation, not as a confirmed working calculator built by Leonardo. Its appearance in the Codex Madrid manuscripts became widely discussed after those notebooks were rediscovered and published in the 20th century. Historians remain cautious about assigning modern capabilities to the incomplete drawing.

It was not a computer in the electronic sense and should not be confused with a slide rule, which performs calculations through calibrated scales rather than interlocking gears. Leonardo’s design belongs to a long history of calculating devices that later included Pascal’s calculator and other mechanical adding machines.