Recently, a hierarchical sequence of augmented basis sets of double, triple, and quadruple zeta valence qualities plus polarization functions for the atoms from H to Ar was generated. At the B3LYP, PBE1PBE, M06, and M06-2X levels, we report a systematic study of Gaussian basis set convergence on frequency dependent optical rotation ([alpha]omega) calculations of thirteen rigid chiral molecules at their equilibrium geometries. By direct calculations or by fitting the directly calculated values through one extrapolation scheme, estimates of complete basis set (CBS) limits were obtained. These CBS limits can be used as reference values to calibrate further DFT calculations. (C) 2010 Elsevier B. V. All rights reserved.