What is the SI unit of electrical resistance?

The SI unit of electrical resistance is the ohm. This unit is defined as the electrical resistance between two points of a conductor when a constant potential difference of one volt applied between those points produces a current of one ampere. Essentially, the ohm quantifies how much a material opposes the flow of electric current; a higher resistance means less current flows for a given voltage.

In contrast, amperes measure the flow of electric current, volts measure the potential difference that drives that current, and watts measure electrical power, which is the rate at which electrical energy is transferred. These units each have distinct roles in the context of electrical circuits, underscoring why the ohm specifically identifies resistance.