Kilo-volt-ampere is called as KVA. Acquiring of electrical capacity of wiring and circuit breakers are done using this KVA which is the unit of apparent power. 1000 volt-ampere is called as one kilo-volt-ampere. Here is the KVA formula for single and three phase transformer which guides you to calculate the single phase and three phase. Substitute the values of volts and amps in the formulas to calculate the KVA for the single and three-phase transformer.