What range of numbers can Roman numerals represent?

Standard Roman numerals cover 1 to 3999. There is no symbol for zero and no single standard symbol above M (1000), so 3999 (MMMCMXCIX) is the largest value writable without overline notation for thousands.

How does subtractive notation work?

When a smaller symbol comes before a larger one, it is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400, and CM is 900. This avoids long runs of four identical symbols, so 4 is written IV rather than IIII.

Why does the tool reject IIII or VV?

Those are not well-formed standard numerals. I, X, C, and M may repeat at most three times in a row, and V, L, and D may not repeat at all. The validator rebuilds the canonical numeral and rejects inputs that do not match it, like IIII (which should be IV) or VV (which should be X).

Why are there no fractions or zero?

The Roman system was designed for counting and tallying, not place-value arithmetic, so it has no concept of zero and no standard whole-number fractions. Modern usage keeps it to positive integers in the 1 to 3999 range.

Where are Roman numerals still used today?

They appear on clock faces, in book chapter and volume numbering, for movie sequels and Super Bowls, in regnal names like Elizabeth II, and on building cornerstones to mark the year. The converter handles all of these everyday cases.

Roman Numeral Chart — Gera Tools

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Roman numerals encode numbers using seven letters whose values are added or, in specific pairs, subtracted. This tool converts integers to Roman numerals and back, and it validates Roman input so malformed numerals are caught rather than silently misread.

How it works

Number-to-Roman uses a greedy algorithm over a fixed value table that includes the six subtractive pairs. It repeatedly appends the largest numeral that does not exceed the remaining value:

1000 M   900 CM   500 D   400 CD
 100 C    90 XC    50 L    40 XL
  10 X     9 IX     5 V     4 IV     1 I

Roman-to-number scans the string from right to left: each symbol is added unless it is smaller than the symbol to its right, in which case it is subtracted (so the I in IX is subtracted). To guarantee the input was well-formed, the tool then converts the result back to a canonical numeral and compares; if they differ — as they would for IIII or IC — it reports the input as invalid and shows the correct form.

Example and notes

The current year 2026 is MMXXVI: two thousands (MM), two tens (XX), a five (V), and a one (I). The subtractive rule keeps numerals short — 1999 is MCMXCIX, not a long string of identical letters. The validator enforces the real rules of the system: I, X, C, and M may repeat up to three times, while V, L, and D never repeat. Anything outside 1 to 3999, or any letter beyond I, V, X, L, C, D, M, is rejected with an explanation.