Roman numerals, both directions
Roman numerals still show up on clock faces, book chapters, film credits, building cornerstones, Super Bowls and the years carved over doorways. This converter works both ways: type a number from 1 to 3999 and get its numeral, or type a numeral and get the number — with the value of every piece shown, so you can see how the answer is assembled rather than trusting a black box. Invalid numerals are rejected with the rule they break, instead of being silently misread.
The system in one table
Symbols add up left to right, largest first — except for the six subtractive pairs, where a smaller symbol before a larger one subtracts: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Only three subtractions are allowed (I, X and C do the subtracting, each only before the next two larger symbols), and I, X, C and M may repeat at most three times; V, L and D never repeat. Those two rules make every number from 1 to 3999 have exactly one correct spelling — 49 is XLIX, never IL.
Why the range stops at 3999
With no symbol above M (1000) and a three-repeat limit, the largest standard numeral is MMMCMXCIX, 3999. Larger values were written with an overline (vinculum) multiplying a numeral by 1000, but that notation is not part of the everyday system and is not used here. There is also no Roman zero — the system was built for counting and recording, and zero as a number arrived in Europe much later via Arabic numerals, which is ultimately why we calculate in digits and keep Roman numerals for ceremony. This tool sits in the Date category because its most common real use is years: carving, copyright and commemorative dates like MMXXVI for 2026.
Worked example
2026 converts to MMXXVI (1000 + 1000 + 10 + 10 + 5 + 1), and 49 converts to XLIX — XL for 40, then IX for 9.
How to use this calculator
- Choose the direction: number to Roman, or Roman to number.
- Type the value in the matching field.
- Read the conversion in the green panel.
- Check the piece-by-piece table to see exactly how the numeral is assembled.
Reading years on buildings and films
The classic party trick: split the numeral into thousands, hundreds, tens and ones chunks and read each in isolation. MCMXCIV (a famous film year) splits as M (1000) + CM (900) + XC (90) + IV (4) = 1994. Super Bowl numbers dropped Roman numerals for one year only — Super Bowl 50 — because "Super Bowl L" looked odd to the league; the numerals returned the next year with LI.