The system of Roman numerals uses letters to represent numbers, an idea that was developed by the Phoenicians two thousand years before the founding of the city of Rome in the mid-8th century BCE. Roman numerals as commonly used today are represented by combinations of seven symbols from the Latin alphabet.

Convert to Roman:

Convert from Roman:

 

SymbolIVXLCDM
Value1510501005001000

There was no symbol for zero, a major difference between the Arabic numerals in common use today and the Roman numeral system.[1]

The mathematician Georges Ifrah has described the Roman system as a “prehistoric fossil”,[2] but it nevertheless continued in use throughout Europe, with some modifications, well into the Late Middle Ages. Roman numerals are still used today in certain niche areas such as the regnal numbers of kings and queens, as in King Charles III.

Arithmetic

It has been widely believed that the Roman numeral system is so primitive as to make anything beyond simple addition and subtraction almost impossible, although that view has been challenged.[1] The Romans usually performed their calculations using an abacus,[3] but the methods they used for written calculations are unrecorded.[1]

References

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Bibliography

Erbes, Edward F. “Arithmetic and Roman Numerals.” Mathematics Today, vol. 59, no. 4, Aug. 2023, pp. 118–19.
Ifrah, Georges. The Universal History of Numbers: From Prehistory to the Invention of the Computer. Translated by David Bellos et al., The Harvill Press, 1998.
Kennedy, James G. “Arithmetic with Roman Numerals.” The American Mathematical Monthly, vol. 88, no. 1, Jan. 1981, pp. 29–32, https://www.jstor.org/stable/2320707.