What type of compass did Leonardo da Vinci design for scaling drawings and measurements?

Leonardo da Vinci designed a proportional compass for scaling drawings and measurements.

A proportional compass has two arms joined at a movable pivot. By adjusting the pivot, the user can compare distances and transfer them at a chosen ratio. This made it useful for enlarging or reducing drawings while preserving their proportions.

Leonardo’s work in painting, architecture, anatomy, and engineering required accurate relationships between parts. A proportional instrument could help an artist or engineer move measurements from one scale to another without calculating every value separately.

This tool should not be confused with a magnetic compass, which indicates direction. Nor is it simply an ordinary pair of drawing dividers. The proportional compass is a specialized measuring device whose adjustable geometry controls the relationship between the distances taken from its two ends.