The aims of this study are to evaluate the measurement capability of the electromagnetic power and to understand the current state of standard maintanance of the eight participants among the thirteen national calibration and test organizations. The calibration factors were measured at six test frequencies, 50, 100, 500, 1000, 5000, 10000 MHz by organizations and KRISS on the basis of round robin test. The results were analyzed by calculating the standard deviation of the measured values from the standard values. The analysis shows good agreement within 1.0% for all participants at the measurement frequencies. Therefore, the measurement capability of all participants is good in the frequency range of 50 MHz to 10 GHz. For the four participants which specified standard deviations of repeated measurements in their reporst, the total uncertainties is less than 1.9% at the measurement frequencies.