Non-decimal currencies

A non-decimal currency is a currency that has sub-units that are a non-decimal fraction of the main unit, i.e. the number of sub-units in a main unit is not a power of 10.

Today only two countries in the world use non-decimal currencies. Both of these countries are in Africa. These are Mauritania (1 ouguiya = 5 khoums) and Madagascar (1 ariary = 5 iraimbilanja). However these are only theoretically non-decimal, as in both cases the value of the main unit is so low that the sub-unit is too small to be of any practical use and coins of the sub-unit are no longer used.

The official currency of the Sovereign Military Order of Malta, which retains its claims of sovereignty under international law and has been granted permanent observer status at the United Nations, is the scudo. The scudo is subdivided into 12 tarì, each of 20 grani with 6 piccioli to the grano. It is pegged to the euro (at a rate of 1:0.24).

All other contemporary currencies are either decimal or have no sub-units at all.

Historically, the use of decimal sub-units was the exception rather than the rule. Decimalised currencies show an advantage in accounting, because amounts are written down and calculated using the decimal numeral system (but when another numeral system is used, such as the vigesimal system that was common among ancient Mesoamerican civilizations or the sexagesimal system used by the ancient Mesopotamians, this advantage disappears). However, decimalised currencies also have disadvantages. The principal advantage of most non-decimal currencies is that they are more easily divided, particularly by numbers such as 3 and 8, than decimal currencies. A currency with 100 minor units to the major unit is divisible neither into 3 nor into 8, and furthermore 100 may be an uncomfortably large number for some poorly educated people to deal with. For example, one-third of an Austrian Gulden (of 60 Kreuzer) was 20 Kreuzer while a third of a dollar is 33.333 cents. This divisibility is useful when trading and when sharing out sums of money. For these reasons, many states chose in the past to adopt non-decimal currencies based on divisions into sub-units such as 12 or 20, sometimes with more than one tier of sub-units.

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Wikipedia