Hamaker constants represent the London Dispersion Force of the van der Waals attraction between two materials. London Dispersion Forces arise from the interaction between fluctuating dipoles whose frequencies lie in the optical and UV regions of the spectrum. Therefore, Hamaker constants may be calculated from the complex dielectric constants measured in the optical/UV portions of the spectrum. Gecko Hamaker program calculates a London Dispersion spectrum for each input material spectrum. Using the London Dispersion spectra, the program will calculate retarded Hamaker coefficients for layers of thin films. At present, the number of layers is limited to 99.