To calculate the amperage of copper wire, divide the total wattage by the voltage of the system. Wattage is the sum of the electrical power of all devices in the circuit, and voltage is the electrical force of the circuit.

Amps are the unit of measurement used to define the amount of current used in a given circuit. Aside from voltage and wattage, factors like the gauge of the wire and wire type can affect the amperage of a system. Due to these components, circuits are regulated with specific wiring requirements to avoid overheating.

The exact voltage of a system can be determined by using instruments such as a voltmeter, digital multimeter or an oscilloscope. Standard circuits typically function at either 110 or 220 volts, but in the case that the voltage is unknown and unpredictable, any one of these instruments are necessary. Watts are the measurement of how the energy is used in a circuit. If multiple devices exist in a system, the total wattage is the sum of all of the electrical devices' wattage. Once the voltage and the wattage have been defined, the amperage can be determined via the equation voltage divided by wattage equals amperage.