k0 Calculator uses complex numbers either in polar or rectangular form (magnitude and phase, or real and imaginary components). Input in one format is automatically converted to the other. Result is given in both formats. The calculator designed to calculate the k0-factor for distance relays. The k0 factor is defined as k0 = ( ZL0 - ZL1) / ( 3* ZL1), where ZL0 and ZL1 are the zero and positive sequence impedances of the transmission line to be protected.