You're reading The Three Musketeers, and learn that d'Artagnan arrived in Paris with only fifteen "écu" in his pocket, and that three of them are are apparently worth nine "livre". Later, he receives 40 whole "pistoles" as a reward. Is that a lot of money? How many écus are in a pistole? And then, when you set down the Three Musketeers and watch your disc of Les Misérables, suddenly there's not an écu to be seen and they're all about "Francs" and "sou". You look these up on a modern currency exchange, and see that the only "Franc" around anymore is used exclusively by Switzerland; France uses only the Euro. Now what?
Unlike Old British Money and American Money, the French didn't stick with one currency system through their whole history. Not only did the buying power of these old currencies change over time, but they changed in value relative to one another depending on what century you found yourself in.
The first French monetary unit was the livre, introduced all the way back in 781 A.D. under Charlemagne. It was equal in value to 1 troy pound of silver. It was subdivided into 20 solidi (later nicknamed "sol" or "sou"), each of which was further subdivided into 12 denarii (deniers).
If this system sounds familiar, that's because it was later used as the basis for Britain's system of pounds, shillings, and pence, right down to the letters "L", "s", and "d". The French for "pound" is actually "livre".
Initially, each duchy in France minted its own livres, but eventually the livres minted in the city of Tours became the standard, and the livre tournois became the official unit of national accounting in 1200 A.D..
The livre remained the official currency unit up until 1577, when it was superseded by:
The first écu, (literally "shield", from the shield design on its reverse) called the écu d'or (gold écu), was ordained by King Louis IX around 1250, when he returned from The Crusades. It was a gold coin worth about the same as a livre tournois. He also started minting a silver coin called the gros tournai, which was worth about the same as a sou.
Over time, though, the écu slowly became devalued. The coins got smaller and smaller. Eventually, the écu d'argent (silver écu) came onto the scene, since it was no longer worth it to make these coins out of gold.
The livre continued to be used, but its value declined along with the écu. Finally, King Louis XIII stepped in and replaced the écu with two coins:
- The Louis d'or (gold Louie), valued at 10 livres; and
- The Louis d'argent (silver Louie), valued at 3 livres.
As often happens in linguistic evolution, the new Louis d'argent coin, frustratingly, soon became known as ... the écu.
As for the Louis d'or, it became known as:
The Louis d'or was an exact copy of the Spanish doubloon, containing 6.7 grams of gold.
This system of pistoles (10 livres), écus (3 livres), livres, and sou (1/20 livre) continued pretty much unabated right up until The French Revolution. Wanting to do away with anything resembling a monarchy, every coin with a king's picture on it was ditched, and in their place arose:
The word "franc" had been used as a euphemism for certain livre tournais coins as early as 1360. When The French Revolution rolled around, it was a natural term to adopt for their new currency. note
Initially, the franc had a value almost equal to the old livre. It was a coin containing a net 4.5 grams of silver. Officially, it was divided into 100 centimes; unofficially, the old term "sou", meaning 1/20 of a livre, quickly came to mean 1/20 of a franc.
In World War I, France left the gold standard, and the franc dwindled in value. By 1934, its value was only 17% of what it was in 1915; by 1959, it was worth only 2.5% of what it was in 1934. Finally in 1960 they'd had enough, and replaced the franc with the nouveau franc (NF) at a rate of 100 old francs to the new franc. This in turn continued to lose value, until in 1999 the (new) franc was worth less than 1/8 of what it was in 1960.
The end of French currency
In 1999, France, as a member of The European Union's "Eurozone", officially adopted the Euro () as its unit of currency. Francs were converted to euros at a rate of exactly 6.55957 francs to 1 euro. Euro coins and bank notes were released in 2002.
Today, the "sou" no longer refers to any particular coin, but is merely a generic term for money, roughly comparable to "change". In Quebec, however, a sou means a Canadian cent—as the old royal sou was approximately equal to the British ha'penny when the British rolled in. That said, confusingly, a "thirty-sou piece" is a quarter, i.e. 25 cent piece, because before Canada adopted decimal currency, it tried using a native Canadian pound valued at exactly 1 pound for 4 U.S. dollars (the exchange rate for sterling was slightly more than 4 dollars to the pound). The result was that 1 U.S. dollar was worth 5 shillings Canadian meaning that 25 cents was worth 1 shilling 3 pence, which is 15 pence, which is 30 ha'pennies, or 30 sous. The name transferred over to the Canadian quarter when Canada adopted its own native dollar even though sou in general became the word for the Canadian cent.