Roman Numeral Converter — Numbers to Numerals and Back
Convert any number to Roman numerals and any numeral to a number — with the bar notation above 3,999 and strict checking of malformed numerals.
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Reference table
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Convert between numbers and Roman numerals in either direction, instantly as you type. Numbers from 1 to 3,999,999 are supported, using the traditional bar (vinculum) over a numeral to multiply it by a thousand. Numerals are validated strictly by default, so IIII, VV and IC are flagged with an explanation rather than silently accepted — with a lenient mode for clock faces and old inscriptions that break the rules.
How to use Roman Numeral Converter
- Type a number in the left box, or a numeral in the right — the other updates as you type.
- Tap a year chip for common dates, including the current year.
- A message explains anything unusual: subtractive pairs, the bar for thousands, or why a numeral is invalid.
- Copy numeral puts it on the clipboard, bar included.
The rules in one paragraph
Seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. Letters are written largest first and added — except that a smaller letter placed before a larger one is subtracted, and only six such pairs are allowed: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900). I, X, C and M may repeat up to three times; V, L and D never repeat. So 1994 is MCMXCIV: M (1000) + CM (900) + XC (90) + IV (4).
Beyond 3,999
With three Ms the largest classical numeral is MMMCMXCIX. For larger numbers the Romans drew a bar over a numeral to multiply it by a thousand — V̅ is 5,000, X̅ is 10,000, and 2026 is MMXXVI whereas 2,026,000 is M̅M̅X̅X̅V̅I̅. This converter writes the bar with the Unicode combining overline, which pastes as plain text; when typing a barred numeral yourself, put the barred part in parentheses, (IV)CMXCIX, or after it an underscore, IV_CMXCIX.
Why strict checking matters
Many converters will happily read IIII as 4 and IC as 99. Both are wrong by the standard rules, and if you are checking a tattoo, an engraving or a movie copyright date, a converter that accepts anything tells you nothing. Strict mode enforces the canonical form and says which rule was broken. Lenient mode exists because the real world is messy: watch and clock faces traditionally show IIII (for visual balance with VIII opposite), and Roman inscriptions used all sorts of variants.
Where you still meet them
Copyright years in film credits (MMXXVI), Super Bowls (LX), monarchs and popes (Charles III, Leo XIV), book chapters and outline numbering, clock faces, and building cornerstones. The BBC and film studios used them precisely because they are hard to read at a glance — dating a rerun takes a moment's arithmetic.
For other number systems, see the number base converter.
Frequently asked questions
Is there a Roman numeral for zero?
No. The system is additive and had no symbol for nothing; medieval scholars used the word nulla when a zero was needed in tables. Numerals start at I = 1, and there are no negatives or fractions in the standard form.
Why is IIII on clocks if it is wrong?
Tradition and balance: IIII visually matches VIII on the opposite side of the dial, and the convention dates back centuries. It is a recognised exception, not standard notation — which is why strict mode flags it and lenient mode accepts it.
How do you write numbers over 3,999?
With a bar (vinculum) over the part to be multiplied by 1,000: V̅ = 5,000, X̅ = 10,000, M̅ = 1,000,000. The converter writes the bar with a Unicode overline; to type one, use parentheses for the barred part — (XII)CDLVI = 12,456.
What is 2026 in Roman numerals?
MMXXVI: MM (2000) + XX (20) + VI (6). Film credits and building dates use exactly this form.
Why is IC not 99?
Subtraction is only allowed for I before V or X, X before L or C, and C before D or M — one step down. 99 is XCIX (90 + 9). IC, IM and XM are common mistakes the strict checker catches.