Voltage ratings are evaluations based on research and experimentation that help to determine how much voltage can be safely utilized by a particular form of wiring. The voltage rating will take into consideration the materials used to construct the wiring, the thickness of the actual cable design of the wiring, and the intended use of the wire. A scale of voltage rating is established for all forms of electrical wiring in use today.

The main function of a voltage rating is to ensure that the user of the wiring or the device that contains the wiring can reasonably expect to utilize the material and not encounter danger to self or the device. From this perspective, the voltage rating will specify how much electrical current can safely be carried through the wiring, as well as defining the type of current that can be safely conducted through the wire. Observing the standard set by the voltage rating greatly diminishes the opportunity for overheating and electrical fires.

There is no wired device in use today that has not been tested and certified with a voltage rating. Depending on the construction and intended use of the wiring, the voltage rating may clear the wire for a high amount of voltage. As an example cable voltage ratings for MI cable is usually within the range of one thousand volts. Wiring for table lamps and other household appliances would be much lower.

By setting a voltage rating that specifies the highest amount of current that the wiring can carry and still operate within acceptable safety limits, the voltage rating makes it possible for governments and other jurisdictions to set standards for wiring used in all sorts of applications. Wiring for use in setting up the electrical system for a residential home must meet specific manufacturing standards and be awarded a voltage rating within a given range. The same is true for wiring in public buildings. Many types of machinery used in the production of goods and services must also contain wiring that meets standards and a voltage rating that is considered reasonable for the amount of current the machine will need in order to function long term.