What type of calculating machine did Leonardo da Vinci sketch with toothed wheels?

Leonardo da Vinci sketched a mechanical calculator with toothed wheels.

The design appears in a 1502 notebook drawing and is commonly interpreted as a device for performing arithmetic through linked gear rotations. Turning one wheel would represent a numerical change and could transmit movement to another wheel, creating a system for carrying values between places.

The drawing is important in the history of calculating devices, but it does not prove that Leonardo completed or operated a working calculator. Some scholars have debated exactly how the mechanism was intended to function, and modern reconstructions necessarily make assumptions about missing details.

Leonardo’s sketch predates the well-documented calculating machines of Blaise Pascal and Gottfried Wilhelm Leibniz by more than a century. It should not be confused with an abacus, which uses manually positioned counters, or an odometer, which records distance rather than carrying out general arithmetic.