A tool for medical physicists to calculate x-ray attenuation for shielding. The tool uses the NIST tables of x-ray mass attenuation coefficients. It's like having the NIST tables in your pocket! It can be used to display characteristic information of elements and compounds (x-ray edges, density, linear mass attenuation graph for a mono-energetic narrow x-ray beam) and to calculate the transmission and attenuation through a layer of a given thickness of any material in the database. If you don't like adds or want to support my work, please buy the PRO version.