It is impossible to give even approximate estimates of the purchasing power of late-medieval money. We know from the income-tax returns of 1436 (imposed on incomes of more than £20) that the average income of a nobleman was £865, of a well-to-do knight £208, of a lesser knight £60, of an esquire £24, and of minor gentry, merchants, yeoman and important artisans from £15 to £19. At this date a good ploughman could make perhaps £4 a year, though before the Black Death he might have made as little as 10 shillings.
The English pound sterling of 20 shillings or 240 pence must not be confused with the French pound tournois of 20 sous or 240 deniers. (There was also the pound parisis and the pound bordelaise, but these are not used in this book.) The English mark of silver was worth 13s 4d sterling, the mark of gold £6 sterling. These pounds—sterling and tournois—and marks were all what was termed monies of account. The exchange rate between English and French monies of account was frequently adjusted by the two governments ; in the fourteenth century a pound sterling was usually worth 6 pounds tournois but in the fifteenth century it rose to 9 pounds tournois.
The basic English gold coin was the noble of 6s 8d, originally weighing 7.77 gms but reduced to 6.99 gms in 1412. The French gold coins or crowns were, very roughly, equivalent in weight and value to an English half-noble; they consisted of the mouton, so called because it bore an agnus dei ; the franc ; and the écu. The beautiful Anglo-Gallic salut of the Lancastrians can also be equated with the half-noble, being worth 3s 4d sterling. Where mentioned, the florins of other European currencies should similarly be equated.
Most English troops would have been paid in silver, consisting of the groat (4d), the half-groat, and the penny and its sub-divisions. Sometimes they would have received French silver or base-metal coins instead, such as the gros tournois or the blanc.