The construct herein utilises the Photon mass-energy threshold, as derived by Storti et. al., to facilitate the precise derivation of the mass-energies of a Photon and Graviton. Moreover, recognising the wave-particle duality of the Photon, the root-mean-square (RMS) charge radii of a free Photon and Graviton is derived to high computational precision. In addition, the RMS charge diameters of a Photon and Graviton are shown to be in agreement with generalised Quantum Gravity (QG) models, implicitly supporting the limiting definition of the Planck length.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.