From calculations of semiconductor interface charge, oxide voltage and tunneling currents for MOS systems with equivalent oxide thickness (EOT) in the range of 1 nm, rules are suggested for making it possible to compare leakage quality of different oxides with an accuracy of a factor 2 – 3 if the EOT is known. The standard procedure suggested gives considerably better accuracy than the commonly used method to determine leakage at VFB+1V for n-type and VFB-1V for p-type substrates.