We investigate the size-dependent optical absorption coefficients of CdSe nanocrystals at both the band-edge and high within the absorption profile. The absorption properties in both of these regions must be self-consistent to ensure accuracy of the measured coefficients. By combining transmission electron microscopy and inductively coupled plasma−optical emission spectroscopy, we map out the optical absorption properties and establish reliable size-dependent band-edge calibration curves. The measured absorption properties are compared to a simple 0D confinement model, to classical theory based on light absorption by small particles in a dielectric medium and to state-of-the-art atomistic semiempirical pseudopotential modeling. The applicability of these newly established calibration curves is demonstrated by analyzing the nucleation and growth kinetics of CdSe nanocrystals in solution.