This is a reference for students, teachers and practitioners in engineering, physics, sciences and technical subjects. More than 3500 conversion factors are given; these have been calculated from primary conversion factors agreed internationally. All conversion factors are given to the greatest accuracy possible up to ten significant figures. The conversion factors are grouped into unit types by areas of science, and range from angular acceleration to volume flow. An appendix of agreed primary conversion factors is given. Also of practical help are appendices of common mathematical and engineering formulae.