The systems of coinage used in the middle ages were more complex and more interesting than what's presented in most fantasy role-playing systems: if gold, silver and copper "pieces" with nice metric conversions seemed too neat to you, you were right; read on.
Medieval currencies were based on silver rather than gold. Gold constituted a very small part of the circulation because it was simply worth too much: the few gold coins produced were useful only to nobles and elite business-men who were, in any case, more inclined to use letters of credit, which were safer. In England, no gold coins were issued until late in the period, though some from the continent may have been in circulation. Copper, bronze and other metals were similarly absent, though for the opposite reason: the cost of minting would have oustripped the actual value. Thus the very basis of D&D's tripartate system is ahistorical: all coins of common use would be silver.
Mostly, kings followed Charlemagne's lead, who essentially borrowed the Roman system, and employed a three-denomination system: in England these had the familiar names of penny, shilling and pound, but equivalents were nearly universal, with common abbreviations L, s and d. Western Europe was not on a metric system: 12 pennies equalled a shilling and 20 shilling a pound. Shillings and pounds, however, were concepts only, used in book-keeping: no shilling or pound coins were minted.
And while the d-s-L system was almost universal, it was just the foundation of messy systems that varied geographically and changed frequently. A host of intermediate denominations were conceived and occasionally circulated physically. In England, the groat was equal to four pennies; the farthing one quarter of a penny--but usually made, like the halfpenny, by simply cutting a penny into pieces. It was only in the renaissance that larger denominations, like Crowns and Angels, entered the space between shilling and pound.
Kings issued new coins sporadically and the relative value of deonominations might change over time--much more frequently with gold coins, as the gold-silver exchange rate fluctuated. Debasement was a constant problem, and so the pennies, denarii or pfennigs of one country might be worth far less then those of a neighbor. This established the utility of money-changers, who would keep track of such variety.
Silver pennies were the coin of common use, and should be so for any "adventurers," regardless of stripe. Pennies had significant buying power as far as the peasantry was concerned (the utility of the "silver piece" in D&D is not far off then). It's hard to establish in our minds what a penny was worth by comparison with modern money; hard to say that a penny is worth $1 or $100, though is was somewhere in that range. We've had industrial and green "revolutions," and the relative costs of food, manufactured goods, land, and labour are very different for us as a result.
Today, in the industrialized world, labour is expensive, food and energy is very cheap, and the price of land has much more to do with how good a house will look on it than its arability. In contrast, labour was generally very cheap in the middle ages, while food ate up at least half of all income, usually more. There was little left over for clothing, tools and housing. Thus land was rented instead of bought and misfortune easily brought total ruin, since nothing could be saved. (Speaking here of the peasantry and even townspeople, nobles of course spent differently.)
In 14th century England, refusing to work for one day carried a fine of 3d; alternately, a peasant could be paid back for days he was set to work at a rate of about 1d (depending on time of year). Peasants might have taxable goods (mostly animals and stored food) worth 6s to 6L or more.
By comparing the value of some item today with its value in the middle ages (at some place and time) we can estimate an appoximate exchange rate between penny and dollar.
|item||modern and medieval values||penny value|
|work payment||$60 : 1d–3d||$20–60|
|home value||$120,000 : 10L||$50|
|pig||$80? : 2d||$40|
|cow||$1000–3500 : 9s||$9–32|
|cooking pot||$25 : 0.5d||$50|
|1 acre land||$2,000 : 32d||$62|
Based on the above we could take $40 : 1d as an order-of-magnitude estimate. This gives us some feel for the buying power a penny would posess. Roughly, for other denominations:
A cohesive system
What does all this mean for a fantasy role-playing campaign? Adventurers should generally carry and use silver pennies and farthings. Peasants may trade in such coins, but perhaps will never see specie at all, complicating interactions with them.
Carrying large sums of money is impractical, so these must be hoarded or deposited with someone trust-worthy: a merchant, local clergeyman or, if the adventurers are very famous, a lord. Major purchases will likely be made through this person, via letters of credit or other agreements, which take time to communicate.
Plundered coin hoards will be unusable, especially if old: adventurers will have to visit a money-changer or other merchant to accept the metal for its own worth—with a fee, of course. Travel will also require such conversion. And the foreignness of another county's coinage will enhance the flavor of the game; an effect that should generally acompany more realistic, complex systems of coinage.
(This article is part of a series, Sensical Fantasy.)