This question quotes Terry Pratchett's claim:

The British resisted decimalized currency for a long time because they thought it was too complicated.

Is this a fair comparison with its inference that British currency was significantly more complex than decimal currency?

Or is it a simple matter of lack of familiarity leading to misunderstanding?

For purposes of comparison, even though it is a century earlier, the era of interest I believe is best taken from 1800 to 1850, early to mid 19th century. Both the U.K. and U.S. are then on a metallic currency standard, and the smaller coins in both currencies still retain real buying power. I believe this provides a better comparison than latter time periods, say after the Second World War, would.


Although I have posted an answer below, I have no intent to accept it. The material there is posted as a resource for any and all who would care to attempt a definitive answer.


  • Comments are not for extended discussion; this conversation has been moved to chat. – Mark C. Wallace Feb 2 at 15:04
  • For a good overview of British currency pre-decimalisation see youtu.be/R2paSGQRwvo It turns out to be surprisingly rational. – DrMcCleod Feb 3 at 18:24
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    One of the big drivers for decimalisation was the use of computers for accounting. Big companies needed to computerise to compete, but they couldn't buy off-the-shelf computers and accounting programs that worked for the rest of the world because of our weird currency. At one point ICL produced machines which had special hardware for sums with UK money, but IBM weren't going to do that. International trade was similarly complicated. Hence a drive to switch to something that the rest of the world understood. – Paul Johnson Feb 4 at 14:46
  • @PaulJohnson: Exactly - There wouldn't have been enough baloney to slice to make the programmers millionaires if the currency unit had that many divisors. – Pieter Geerkens Feb 4 at 17:23
  • @PieterGeerkens Other than in Star Treck, most people at that time were unaware that computers existed. It certainly played no role in public discussions. Internaly they probably used pennies, with input/output functions to make the sums 'readable' for humans. – Mark Johnson Feb 4 at 20:20

[Another] question quotes Terry Prattchett as:

"The British resisted decimalized currency for a long time because they thought it was too complicated."

Is this a fair comparison with its inference that British currency was significantly more complex than decimal currency?

No. The quote is from Good Omens, by Terry Pratchett (not Prattchett) and Neil Gaiman. It's a humorous work and the quote is an ironic joke, not a factual claim. Of course the process of changing over was complex even though the new system was simpler. (Wikipedia seems very prim, with its continual mentions of Decimal Day. In practice, it was known as D-Day, to cash in on the historical allusion to WWII.)

I'm old enough to have used both systems. Whilst the pre-decimalisation system was objectively more complex with its base 12 and base 20 calculations than an all base 10 system, using £sd coins was no harder for day-to-day transactions for those familiar with it than using decimal coinage. More involved activities, such as working out interest rates, were complicated by having to work in multiple bases but for everyday work this was offset by the extra factors available working in base 12 rather than base 10. (⅓ of 2/- -> 8d. ⅓ of 10p -> oops.) Plus we kept up our mental arithmetic skills by not having calculators.

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    Good find. I simply copied that from the references question, so you should point out that correction there as well. – Pieter Geerkens Feb 2 at 1:12
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    Working with pre-decimal currency may have been easy for people who grew up using it, but I'd bet it was fairly baffling to tourists and immigrants... – user3153372 Feb 2 at 10:13
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    When in foreign climes, I tend to proffer my wallet to the vendor, who then proceeds to select a few notes and return me a few coins. Works every time. – Mawg says reinstate Monica Feb 2 at 10:29
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    @user3153372 "baffling to tourists" is an interesting point; the British Lsd system is famously adapted from the Latin "librae, solidi, and denarii", though the ancient Roman system was actually rather different and I think the English Lsd came from the Franks. At one stage similar divisions were widespread throughout Europe: 1 livre = 20 sols/sous = 240 deniers in pre-revolutionary France, for example, but with national variations, e.g. Dutch 1 gulden = 20 stuivers = 160 duit = 320 penningen, Ottoman 1 kuruş = 40 para = 120 akçe. See e.g. en.wikipedia.org/wiki/Non-decimal_currency – Silverfish Feb 2 at 20:27
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    @chepner that's a very US-centric view. In Britain unlike the US, for a time we kept up quite well with the pace of converting notes to coins when inflation justified it. So where your largest coin in common usage (ignoring the dollar and half dollar which are rarer) is worth 18p, our largest coin in common usage is worth £2. As you can imagine lots more people in Britain will pay for things with coins. (Though of course with the advent of contactless cards and COVID lots of people are now using coins and cash less). – Muzer Feb 3 at 0:08

Here is a comparison chart with rough equivalences between coin values. I've matched coins at an approximate ratio of "1£ : $4" as covering both coin ranges and approximating the exchange rate of the time.

s. / d.1 Pence Equiv. Coin / Note Name U.S. Value Cents Equiv. U.S. Coin
0 / ⅛ ⅛ d. Half-Farthing - - -
0 / ¼ ¼ d. Farthing $0, ½₵ ½₵ Half Cent
0 / ½ ½ d. Ha'penny (Half-Penny) $0, 1₵ 1₵ Cent (Penny)
0 / 1 1 d. Pence - - -
0 / 2 2 d. Tuppence (Two-Pence) $0, 5₵ 5₵ Half Dime (later Nickel)
0 / 3 3 d. Thruppence (Three-Pence) - - -
0 / 4 4 d. Fourpence (Groat) $0, 10₵ 10₵ Dime
0 / 6 6 d. Sixpence (Tanner) - - -
1 / - 12 d. Shilling or Bob $0, 25₵ 25₵ Quarter
2 / - 24 d. Florin $0, 50₵ 50₵ Half Dollar
2 / 6 30 d. Half a Crown - - -
5 / - 60 d. Crown (Five Shillings/Bob) $1, 0₵ 100₵ Dollar
10 / - 120 d. Ten Bob (Note) $2, 50₵ 250₵ Quarter Eagle
20 / - 240 d. Sovereign (£) $5, 0₵ 500₵ Half Eagle
21 / - 252 d. Guinea (Coin) - - -
- - - $10, 0₵ 1000₵ Eagle
- - - $20, 0₵ 2000₵ Double Eagle

As can be seen, both currencies covered this range of value with 12 and 11 distinct coins respectively, many with unique names, in approximately the same ratios to each other. I've always been more familiar with the decimal system, but I see neither has being inherently more or less complex than the other, given equal familiarity.


  1. Standard British abbreviation for "Shillings and Pence"
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    The abbreviations comes from: denarius 1/240 ; solidus = 12 denarii ; libra = 20 solidi – Mark Johnson Feb 1 at 21:19
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    [from his biography] Baron of Mauá, the first Brazilian industrialist in the XIX c., started as a poor office boy inside an import firm. After studying math at night, he could make calculations in pounds/s/d/etc. British merchants in Rio de Janeiro often exploited their counterparts' lack of math skills or knowledge of the Imperial system to make a rounding "error" and get a few extra $. Thus, his boss was happy when he noticed that the English could not fool that boy, and promoted him. – Luiz Feb 1 at 22:08
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    Amounts would be written without embedded spaces and 0d would be shown as a hyphen. So the value of a florin (a tenth of a pound) would be written as 2/-. When spoken the forward slash would be pronounced as "and". "Pence" would be omitted for amounts over a shilling, so the value of a half crown would be pronounced as "two and six". – Graham Nye Feb 2 at 1:47
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    @Pieter If I pay for a £10.05 item with a £20 note and a 5p coin a young sales assistant will stare at me as if I'd grown a second head. Conversely if I paid for the same item with just the £20 note an older assistant will ask me "have you got the 5?" in order to avoid counting out a handful of change. – Graham Nye Feb 2 at 15:25
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    Better. Unofficially, post-decimalization, was the Maggie (the new £1 coin in the 1980s). Because it was thick, brassy, and thought it was a sovereign. – Brian Drummond Feb 2 at 17:42

My Grandmother, who was a teacher, said that adults back then naturally thought in fractions and not decimals. You've got to consider there were no pocket calculators and for both mental arthritic and abacuses divisions in terms of ratios of natural numbers. Everything someone experienced growing up in those days: Measuring devices (no digital scales then, scale weights came in fractions), clocks, coinage was in fractions. Units were in base 12, 14 or 20 because they divided nicely into more numbers, how often did you multiply or divide by 10 back then?

There was plenty of people who "didn't get" decimals, no joke. These days with pocket calculators and decimal currency children grow up dealing with decimals and now find fractions the harder of the two (look the difficulty they have with clock times) but that wasn't always the case.

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    A lot of it is just familiarity. E.g. people who grew up with the metric system probably find all those confusing prefixes (centi, milli, micro &c - all the way from yocto to yotta) to be second nature, and think that sensible US units are confusing. And vice versa, of course :-) – jamesqf Feb 3 at 16:45
  • Nice! Even today the representation of many irrational numbers, such as surds, can be and often is expressed to infinite precision with a (repeating and finite) continued fraction rather than with the irregular decimal expansion. This can be a great memory saver in computere programs for example. – Pieter Geerkens Feb 3 at 17:19
  • Shouldn't "mental arthritic" be in fact "mental arithmetic" ? Interesting lapsus lingae... – Jean Marie Becker Feb 3 at 17:47
  • It is not all arbitrary, as the metric system is not just decimals. Think about a swimming pool of 10m x 10m x 1m. How much does the water weight? What is its the volum in liters? Easy: it has 10x10x1 m^3, that is 100m^3, that is 100.000 liters. As 1m^3 = 1 ton, the water weights 100 tons = 100.000 kg, exactly. Now, do the same with 10x10x1 but with yards, pounds, feet^3.... Another example, one liter of milk weights 1 kg, and its volume is 10x10x10 cm or 0.001 m^3. I think the universality and interchangeability of the SI units are the best about the metric system, not the decimality itself – Luiz Feb 3 at 19:34
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    @Luiz: But why on Earth would I want to weigh the water in a swimming pool? And one liter of milk does not weigh 1 kg (whole milk, anyway, I can't speak to the nonfat stuff). If you ever get non-homogenized milk straight from the cow and let it sit for a bit, you'll see that the cream separates and comes to the top, because it's lighter. – jamesqf Feb 4 at 4:48

I was there. (1960s) It was not confusing. Divide one old pound by three is 6/8. (six shillings and eight pence.) Divide a modern pound or a dollar by three and...

The same goes for multiplication. Three jam doughnuts at fourpence is instantly a shilling.

Having distinctive coinage made things easier still. 7/6 is three half-crowns (Instant after nearly 50 years) or if you gave a ten-bob note you'd expect one as change.

  • The similar sizes of half-crowns and florins was not helpful – Henry Feb 3 at 10:12
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    I guess the question is why would you need to divide a pound by 3? – Tim Feb 3 at 12:30
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    if there are three of you @Tim – JCRM Feb 3 at 14:46
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    @Tim If a pound contains 240 pence then dividing it by 5 gives you 48 pence. – Baz Feb 3 at 14:50
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    4 shillings or 2 florins, surely, @Baz? – JCRM Feb 3 at 14:53

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