Whether you're thinking in terms of yards or angstroms, cubits or carats, conversion will be no problem with these useful tables in hand. Johnstone provides units of linear measurement, volume, mass, time, pressure, electrical capacity, and God knows what else. There are even musical units (do you know a crotchet from a semibreve?). Take an inch and Johnstone will give you 25,400.05000 microns.