Roman numerals
Converts Arabic to Roman numerals and back, shows a step-by-step breakdown. Range 1–3999, reference table of symbols, notation rules and famous dates written in Roman.
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Converter and breakdown
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Symbol reference
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Famous dates in Roman numerals
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About Roman numerals
The Roman numeral system originated in Ancient Rome around the 8th century BC and was used throughout the history of the Roman Empire. Unlike the familiar decimal system, it is not positional: the value of a symbol does not depend on its position, but is determined by the symbol itself and its neighbours.
Roman numerals have survived to the present day — we see them on clock faces, in chapter and century numbering, and in the names of monarchs and popes.
Notation rules
- A symbol repeats at most three times in a row: III = 3, but 4 is IV, not IIII.
- A smaller symbol before a larger one is subtracted: IX = 10 − 1 = 9.
- Only I, X and C can be subtracted — and only from the two next-higher symbols.
- V, L and D are never repeated and never used for subtraction.
Origin of symbols
EtymologyI = tally · V = palm · X = two V
I is a tally mark. V is an open hand (five fingers). X is two hands crossed. C comes from Latin centum (hundred). M from mille (thousand). D is half of the old thousand symbol. L may derive from the archaic ↆ.
Zero and positional notation
Differences0 — absent · 3999 — writing limit
Romans had no zero — the system is non-positional, so an empty place had no meaning. They used the word nulla for 'nothing'. This is the key difference from Arabic notation, where zero allows numbers of any size. The maximum in standard notation is 3999 (MMMCMXCIX).
Where used today
PracticeXXI century · Chapter IV · Louis XIV
Centuries (XXI century), chapter and volume numbering, names of monarchs and popes (Elizabeth II, Benedict XVI), clock faces, Olympic Games, Super Bowl, school year designations. In programming — sometimes for stages and versions.
IIII instead of IV
Curiosityclockmaker's four: IIII, not IV
Clockmakers still write IIII instead of IV — the 'clockmaker's four' — for visual symmetry with VIII on the opposite side of the dial. Medieval rules were less strict: symbols ↀ (CIↃ) for thousand and ↁ for five thousand were also in use.
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Frequently asked questions
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