Refined values are obtained in the present study for the refractive index parameter (n) for ultrathin SiO2 films (less than 8 nm in film thickness, L-ox) and summarized as n = 2.139 - 8.991 X 10(-2) X L-ox + 1.872 x 10(-3) x L-ox(2). This formula was obtained starting from variable angle of incidence ellipsometry data on ultrathin SiO2 films, and a previously derived refractive index parameter formula that was based on independently measured thickness' using Fowler-Nordheim electron tunneling measurements. The new n values are useful for extracting more accurate ultrathin SiO2 film thicknesses from ellipsometry measurements.