The Marteau Currency Converter:FAQ

From Marteau


Louis XIV has bribed London's Tory politicians to promote a peace treaty favouring France, they count the money whilst British Secrets are on their way to Utrecht. Frontispiece to Das auffgeschlossene Cabinet derer Groß-Brittannischen Geheimnisse (1715).

This is a SubPage of the Marteau Early 18th-Century Currency Converter supposed to answer the most frequently asked questions concerning these tools.


How reliable are your exchange rates?

They give the momentary situation around 1700, due to a relative stability of Europe’s currencies at the time they are - for the central currencies involved - quite reliably for the period 1690-1720. With some of the currencies covered the phase of stability reaches far into the 18th century.

The ratio of one Reichsthaler making 2.5 Dutch gulden remained stable even until the introduction of the Euro in 2002. Other rates changed sooner du to the devaluations some of the coins suffered.

It would be challenging to construct a system of conversion tools reflecting the changes between the individual currencies. Our tools offer some changes where individual currencies changed within the system. We should like to offer the set of tools for the whole period 1600-1800 yet it would need a group of economic historians to do this work properly. Initiative is welcome here.

How does one establish early 18th century conversion rates?

Practically with a look at contemporary tables offering these rates. Our tools are designed according to the instructions Gerhard Heinrich Paritius gave (in 1707, 1709 and 1717) in the editions of his book on the mathematical equations involved. He again had based his instructions on circulating Dutch tables. See also our note on the default rates we used where we could not follow Paritius.

Ultimately an assesment of the quality of the circulating coinage lay behind these rates.

In theory 17th and 18th-century coins basically had the value of the gold and silver they contained (plus minting costs). Different coins of the same metal value had to be of same value. Practically one had to acknowledge that the circulating coinage (coins wore off if they were not willfully clipped) did not always match the standards – and that official standards could just as well be gradually lowered (in attempts of certain nations to make money of a circulating coinage they could then change against new less valuable coins).

Can one mix currency units and coins the way your tools do it?

Yes, that is what was done. Major currency units like the pound sterling or the international Reichsthaler were not minted. The authorities declared what amounts of coins were to match them. The rate between two currencies would therefore remain stable as long as the metal values behind the monetary units would remain untouched: 20 shillings made one pound sterling. The amount of fine silver of these 20 shillings was fixed at 111.18g; and that would be the real value of the pound sterling. 9.6g silver made a Dutch gulden. 111.18 Dutch guilders would hence match 9.6 English pounds sterling - artithemtically.

The rate merchants took for granted (reflected by our tools) is slightly different and can be called a market rate: It stood at 9 pounds sterling for 100 Dutch guilders.

Local authorities asked their mints to analyse coins of other nations to verify these market rates every now and then. Isaac Newton thus assessed Europe's leading coins in 1702 as did the authoritios of Nuremberg in 1709. One compared freshly minted "unworn" coins to get the "real rate". Newton would later use his assesment to advise his government to demand 103.25 gulden for 9 pounds sterling when paying the troops at Dunkirk with Dutch money (or to mint money abroad for that purpose in order to strike the better deal). Some Dutch coins would match the 9:100 rate yet others would not. Market rates could differ from the assessed rates,

  • if coins of a certain country were well accepted all around the world (and hence likely to make an exchange above its actual value),
  • if the coinage of a country deteriorated (due to a careless government or due to a government which actually made extra money of the circulating coinage by recoining it with a lower value),
  • if a negotiation behind the deal made another rate attractive (the partner who wants to strike the deal makes it more attractive by granting an interesting conversion rate).

Do not your tools ignore the daily changing rates of Europe's stock exchanges?

Yes they do, but you have to remember that these rates do not reflect changes of the underlying exchange rates. The dayly changes of the rates at which chashless transfers could be performed were produced by the additional transaction costs of the trade with bills of exchange: All the major trading places determined on weekly if not daily observations at which additional costs one could perform transfers of money. Merchants offered these bills in a complex system in which they would ballance their own transactions of goods against the virtual flow of money. One had to observe the market with greatest attention if one did not want to loose one's money in ill timed transactions. The rates to be observed here must not be confused with the rates our conversion tools offer. Our tools offer stable rates of an exchange between currency units – rates backed by the country's coinage and by the official standards at which new coins were supposed to be issued. The changing rates of the trade of bills of exchange reflect the availability of cashless transfers. Our rates do by contrast give money equivalents – which alone allow you to compare prices between countries; they do not tell you how much you actually paid if tried to change money.

Do you want to imply one could actually change Japanese mommes silver into guilders of Geneva?

Yes, though not directly. Japan was, to make this evident, a country of closed borders. No one got out, and no one got in without risking his life. All trade was under strict surveillance – and yet Japan lost the best part of its silver money by trading with China and Korea buying silk and ginseng from abroad without selling anything notable in the exchange – see the article Money (Japan) for details. There was, the authorities had to note, no such thing like an isolated economy. West Africans used cowrie shells as money – difficult to counterfeit, rare enough to serve as money, transportable – and risked an inflation when Europeans discovered that they could get these shells for very little money at India's coast. Silver and gold remained the essence of money circulating on the international market, an asset Europe's powers brought from Copenhagen, London and Paris to India's coasts in order to strike money as needed in India – silver rupees bearing Arabian inscriptions, minted by European specialists on India's soil. (See the more detailed history at Money (India)). One can well say that artisans in Shanghai and Calcutta were ultimately paid with the very same silver circulating on the world’s market since this was what authorities in London and Edo actually observed, eager to prevent an outflow of money, and helpless if this outflow took place as it happened to Japan, or lucky if they effectively reversed affairs as London's specialists did in the 1690s (See Isaac Newton's observations on the world wide flow of gold and silver moneys in his reports as master of the Roayl Mint). It does, hence, make sense to give the equivalents in monies. 32 Florins à Geneve were essentially 37 momme Japanese silver of 80% purity – this is not even a contradiction in terms as the momme was, and still is, nothing but a unit of weight: the amount of 3.75 g silver in this case.

Our conversion tools will most of all be useful where you have to compare prices - and here they will be the more useful the more exotic the currencies involved are. They give equivalents for small and big sums and tell you how accounts were held.

If I have to calculate with other rates than those you give, can I do that with your tools?

Yes, you can change the conversion rates our tools are using at the bottom of each page to make them fit the computations you have to perform according to your document sources. The most interesting modifications will be perhaps those done on the basis of fine metal contents of individual coins involved. Our tools can calculate with fine metal contents provided you feed the data into them. See our special page on silver coins and their fine metal contents for further instruction.

Can't you produce tools for conversions into modern currencies?

Technically this would be simple. Practically it would be a misleading step. Take a book: In London you got a decent novel for a shilling six pence and an expensive one for three shillings and six pence. If you bought your lunch at a street vendor – meat in paper, spiced with mustard, bread and wine with that – nothing special, you would pay as much as you paid for your little novel. Books were cheap then, as cheap as they are today – and yet they were expensive for a day labourer who made 14 pence a day. If you happen to live in an industrialized country today you can be a cleaning woman and earn your book in less than an hour.

Think of the 18th century as a world in which our modern London was surrounded by our modern Bangladesh. People of the surrounding third world country do mean jobs in the city, and those in the country get next to nothing for what they produce. You will then have to deal with at least two price levels of comparable goods. Does this mean: farmers could not buy books? No it does not – just as even people in third world countries buy cars and tv-sets if they can. Even if you know the price you cannot tell whether people are ready to pay it or not.

The sensible thing to be done here is hence: look at lists of prices and wages – and even that will be a problematic thing to do: Modern families are two income families with a kid and no servants. Early 18th century incomes could be household incomes, the incomes of a family plus all the servants it employed. Try to think of economies quite unlike our modern economies (which are – if you live in the western hemisphere you might concede this – based on an exploitation of countries abroad rather than on an exploitation of the lower classes within your country).

If you still feel you'd like to know how much something in early 18th-century money would be today:

Our tools will give you the exchange rates for the first decade of the 18th century (and that means with some currecies for the 18th remaining century).

Technical Questions

Do I have to be on-line to use your tools?

No. The pages on which you perform calculations at our site use simple java scripts to communicate with your browser's calculating functions. We do not see what computations you perform. You can hence use all our tools off-line. Save any page you especially need on your lap top if you have work to do at an archive or library (or contact us for a CD-version of the whole site to be used off-line).

Do your tools also accept decimnalised sums?

Yes they do. If you find such sums in modern books, you can put them into our calculators. Yet be careful if you are a central European user – your browser will require the dot instead of a colon! It is £4.54 and not £4,45.

I put a sum into the form, pressed return and nothing happened

Our tools work in both directions – you have to press the buttons on the screen indicating into which direction you want to change your amount of money.

I am using an Opera browser and get the letters "NaN" instead of sums

This is the "No natural number" notice normal browsers give if you do not feed the form with numbers but with letters for instance. We cannot tell why Opera browsers have this problem, and hope the Opera-people will fix the bug soon.

I have got quite different currencies to handle – can you help?

It will be a pleasure to create the tools you need – if they belong to the 17th and 18th-century world we are interested in. Yet the following tool might be of use to you for whatever unlikely purpose you need it. If you want to, you can use it to change apples into pears on the rate you have found only this very morning on Brussels's fruit market. You might also use it to change money of ancient Syria into money of ancient Rome at a rate valid in 117 A.D. – something like a universal currency converter do be modified on the screen. link

Subpage of the Marteau Platform of Research in Economic History