Roman Numerals Converter
Convert numbers to Roman numerals and back — with strict validation.
Roman numerals are still everywhere: copyright years in film credits (MCMXCIV is 1994), Super Bowl numbering, book chapters, building cornerstones, monarchs and popes (Elizabeth II, Benedict XVI), and clock faces.
How to use
- Type a number on the left (1–3999) to get its Roman form, or type Roman numerals on the right to get the number.
- The Roman side validates strictly: forms like IIII (4) or IC (99) are rejected with an explanation, because clocks aside, they break the standard rules.
About this tool
The system is additive with a subtractive twist: a smaller symbol before a larger one subtracts (IV = 4, XL = 40, CM = 900). With no zero and no place value, arithmetic was painful — but as labels the numerals have outlived the empire by 1,500 years.
This converter covers the standard modern range 1–3999 (MMMCMXCIX) in both directions and validates the Roman side against the canonical rules.
How it works
Roman numerals are built from seven symbols — I 1, V 5, X 10, L 50, C 100, D 500, M 1000 — written largest-first and added. The subtractive rule keeps them compact: a single smaller symbol placed before a larger one subtracts, but only in the six sanctioned pairs IV, IX, XL, XC, CD and CM. That is why 99 is XCIX, never IC.
No symbol repeats more than three times (III, XXX, CCC, MMM), and V, L and D never repeat at all. With those two rules every number from 1 to 3999 has exactly one canonical spelling — which is what makes strict validation, and therefore automatic conversion back, possible.
Worked examples
Film credits: A film ends with “MCMXCIV” in the credits: M 1000 + CM 900 + XC 90 + IV 4 = 1994. Studios liked Roman years partly because the audience cannot read the date at a glance.
Super Bowl numbers: Super Bowl LX is 60: L 50 + X 10. The league briefly dropped numerals for Super Bowl 50 because a lone “L” looked odd in logos — then went straight back to them.
Quick reference
| Symbol | Value | Subtractive pair | Value |
|---|---|---|---|
| I | 1 | IV | 4 |
| V | 5 | IX | 9 |
| X | 10 | XL | 40 |
| L | 50 | XC | 90 |
| C | 100 | CD | 400 |
| D | 500 | CM | 900 |
| M | 1000 | — | — |
Frequently asked questions
Why only up to 3999?
Standard Roman notation has no symbol above M (1000) that can repeat, so 3999 (MMMCMXCIX) is the largest canonical value. Larger numbers historically used an overline (vinculum) meaning ×1000 — V̅ is 5000 — which plain text cannot type reliably, so this converter stays with the standard range and says so instead of guessing.
Why is IIII rejected if clocks use it?
Many clock faces do use IIII for 4 — a tradition explained by symmetry with VIII and by old casting economics. It is a decorative exception, not the standard rule: in text and inscriptions 4 is IV. The converter follows the standard and tells you why.
How do I read a year like MCMXCIV?
Break it into groups: M (1000) + CM (900) + XC (90) + IV (4) = 1994. Read left to right, and whenever a smaller symbol sits before a bigger one, subtract the pair as a unit.
What year is MMXXVI?
2026: MM (2000) + XX (20) + VI (6).
Is there a Roman zero?
No. The system has no zero — medieval scribes later used “nulla” or the letter N for bookkeeping, but classical Roman numerals simply start at I.
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