What device did Leonardo da Vinci design to help calculate multiplication and addition?

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

A calculator mechanism is described in Leonardo’s notes from the late fifteenth century. Its linked gears were intended to represent place values, allowing numerical operations such as addition and multiplication to be performed mechanically. The concept shows Leonardo applying gear trains to abstract mathematical work.

The attribution requires care. Leonardo’s drawings provide evidence of a calculating-machine concept, but no complete calculator built by him has survived. Reconstructions and interpretations differ because the notebook material does not present a modern operating manual.

This device is distinct from Leonardo’s mechanical lion or mechanical knight, which were automaton designs. It is also earlier than electronic calculators by centuries, relying entirely on physical rotation and gear ratios.