Watts Amps Volts Calculator is an easy to use electrical power calculator for converting or calculating to or from Watts, Amps, Voltage, kW or Power Factor. Calculations also include a single phase electrical calculator and a three phase calculator with some helpful hints along the way. Single Phase Calculations. Enter any two values to calculate the third. - Calculate Watts - Calculate Volts - Calculate Amps Three Phase Calculations. Enter any three values to calculate the fourth. - Calculate kW - Calculate Amps - Calculate Volts - Power Factor Single Phase AC or Three Phase AC? Single-phase is the most common system and is mainly used in homes, while a three-phase system is common in industrial or commercial buildings, where heavy loads of power are required. This app is a great companion to our kVA Calculator and Ohms Law Calculator apps.