Roman Numeral Converter

How to use it

1. Type a number to see it in Roman numerals, or type numerals to decode them.
2. Both boxes work at the same time and both directions.
3. Check the chart for the seven basic symbols.

What are Roman numerals?

Roman numerals are a number system, or numeral notation, that builds values from seven letters: I, V, X, L, C, D and M. Symbols add from largest to smallest, and a smaller symbol placed before a larger one subtracts:

MMXXVI = 1000 + 1000 + 10 + 10 + 5 + 1 = 2026

So XVII is 17 by addition, while IV is 4 because the I subtracts from the V. Only six subtractive pairs are allowed: IV, IX, XL, XC, CD and CM. The standard system covers 1 through 3,999, has no zero, and still appears on clock faces, movie credits, monuments and Super Bowl logos.

Worked example

Years in Roman numerals

How Roman numerals work

Roman numerals build numbers from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. You add symbols from largest to smallest, so XVII is 10 plus 5 plus 1 plus 1, which is 17. When a smaller symbol sits before a larger one, you subtract it: IV is 4 and IX is 9. To decode a numeral, compare each letter with the one after it, subtract if it is smaller and add if it is not, so MCMXCIX is 1,000 + 900 + 90 + 9, or 1,999.

The rules that make a numeral valid

Only six subtractive pairs exist: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). You cannot subtract V, L or D, and you cannot skip a tier, so 49 is XLIX rather than IL and 99 is XCIX rather than IC. I, X, C and M may repeat up to three times in a row; V, L and D never repeat. Work through a number one place value at a time: 1,776 is M (1,000) + DCC (700) + LXX (70) + VI (6), which gives MDCCLXXVI, the year carved on many American monuments.

The standard system runs from 1 to 3,999 because there is no single symbol for larger values without a bar notation. A bar (called a vinculum) over a letter multiplies it by 1,000, so a barred V is 5,000 and a barred X is 10,000, but that convention is rare outside textbooks. There is no zero and no way to write fractions, which is a large part of why Arabic numerals replaced Roman ones for arithmetic. The converter checks that a numeral is written the standard way, so it rejects strings like IIII or VX that people sometimes write.

You still meet Roman numerals on clock faces, in movie copyright lines (MMXXVI for 2026), in book prefaces and chapter headings, on monarchs and popes (Elizabeth II, Charles III), and on Super Bowl logos, where the sixtieth game was Super Bowl LX. Birth-date tattoos are another common reason to check a conversion twice before it becomes permanent.

Common uses

• Reading clock faces, book chapters and movie credits
• Writing years and dates in Roman style
• Decoding Super Bowl and monarch numbers
• Homework and history assignments
• Checking a tattoo or engraving before it is made
• Numbering outlines, volumes and appendices

When to use it

• You want to write 2026 in Roman numerals for an invitation or a title page.
• A movie's copyright line reads MCMXCIX and you want the year without counting letters.
• You are double-checking a birth date in Roman numerals for a tattoo.
• Homework asks what XLIV means in numbers (it is 44).
• You are numbering the chapters or appendices of a document in Roman style and want each one right.

Related tools

The Age Calculator pairs well when the numeral you are decoding is a birth year.

The Sum Calculator adds ordinary numbers once you have decoded them.

The Rounding Calculator tidies modern numbers the way numerals never could.