Money in Medieval England and France
Like everything else about the Middle Ages, styles of money varied from place to place, and understanding the relationship between denominations can therefore be confusing. In fact, in the thirteenth century [C.E.], there was only one type of coin in existence: a small, silver piece known in England as a penny and in France as a denier. In England, twelve pennies equaled a shilling (although there were no shillings minted, you simply counted out twelve pennies into someone’s hand); in France twelve deniers equaled a sous (although, likewise, there were no sous in existence). There were, in England, 20 shillings or 240 pennies to a pound sterling; in France there were 20 sous or 240 deniers to a livre. Once again, there was no actual coin struck representing a pound or a livre; to payoff the debt of a pound the debtor handed the creditor a sack containing 240 pennies; in France, to pay off the debt of a livre, the sack would contain 240 deniers. In England, just to make the concept as complicated as possible, they also measured silver by a weight measure called the mark. A mark was two-thirds the weight of a pound sterling, so a mark of silver was the same as 160 pennies. But if the debt was in marks, you didn’t have to supply pennies, a person could use any silver he or she happened to have lying around the house, like a silver plate, just so long as it weighed the right number of marks. When [King Henry III of England] and [Queen] Eleanor promised to pay the pope 135,541 marks to fund [their son] Edmund‘s campaign for the kingship of Sicily, they were promising to pay approximately £90,812, or nearly three years’ income, some of which, presumably, could have come in the form of the royal dining service.…
Just like today, French money and English money differed sufficiently so as to require a rate of exchange. In France, the quality and fineness of a denier (and therefore of a livre composed of those deniers) varied so much that the coins were labeled by location, which is why some of the French sums mentioned in [this book] were specified as livres toumois (minted in Tours, of high quality) and others as livres parisis (minted in Paris, of much lower quality).… The exchange rate in 1265 [C.E.] between livres parisis and the pound sterling was 90 sous (or 1,080 deniers) to the pound. To make it easier, there were 4½ livres parisis to a pound sterling, and 3 livres parisis to a mark. The annual French royal income of 250,000 livres (most likely livres parisis) was therefore the equivalent of about £55,556, a much larger sum than was available to their English counterparts. Henry and Eleanor only had an average annual income of about £36,000.
Anyone who wants to go deeper into this subject should definitely read Peter Spufford’s authoritative and comprehensive work, Money and Its Use in Medieval Europe (Cambridge University Press, 1988), and its complement, The Handbook of Medieval Exchange.