New data based on calculated X-ray spectra for X-ray tubes of different target angles and various magnitudes of kilovoltage ripple are presented. Currently available published data relating the total filtration of diagnostic X-ray tubes to the measured half-value thickness (HVT) are of limited use to those carrying out such measurements. Electronic penetrameters are now widely available, which allow improved accuracy in the measurement of tube kilovoltage, and the monitoring of waveforms. This has highlighted the necessity to refer to data which apply to the correct waveform ripple value, and to the correct tube target angle. A wide range of data referring to 10 degrees and 16 degrees target angles has been calculated. An experimental example is presented where measured values of HVT on nine X-ray tubes are converted to values of total filtration, using the calculated data.