In this paper a new quality indicator for two-tier calibration procedures that use only reflection standards is presented and applied to coaxial-to-waveguide transitions. The quality indicator is based on the algebraic conditioning of the system of equations solved for obtaining transition characteristics. The study has been carried out in a wide bandwidth as a difference with previous works. The obtained results indicate that a threshold value for this indicator around 10% can be established. For values below this limit the error grows to unacceptable values. Additionally, it has been shown that an exponential relationship between quality indicator and the error can be predicted.