StringMash.com

Roman numeral converter

Numbers to Roman numerals and back, with the chart and the rules.

Conversion
32 characters
Updates as you type
Swap to read Roman numerals back

Printable chart
THE SEVEN LETTERS AND THE PAIRS

Roman numeral chart

1I
5V
10X
50L
100C
500D
1000M
4IV
9IX
40XL
90XC
400CD
900CM
2026MMXXVI
3999MMMCMXCIX

Using the converter

Type a number, a year or a whole sentence, and every number from 1 to 3999 is turned into Roman numerals while the words stay put. Letters switches to lowercase, the style used for the page numbers in a book's preface.

Swap to go back. Any word written in numeral letters and valid by the rules is read as a number, so Louis XIV becomes Louis 14. That includes some real words: MIX is M and IX, 1009, and comes out as a number too.

The rules

Seven letters do all the work. I is 1, V 5, X 10, L 50, C 100, D 500 and M 1000, and numerals are written largest first and added up, so MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1.

Six pairs are subtracted instead: IV 4, IX 9, XL 40, XC 90, CD 400 and CM 900. Only I, X and C go in front, and only of the next two letters up, so 99 is XCIX, never IC. No letter repeats more than three times, which is why the standard system stops at 3999.

The converter only reads numerals that follow these rules. IIII, which some clock faces use for 4, is left as it is instead of guessed at.

The Super Bowl that skipped L

The Super Bowl has used Roman numerals since Super Bowl V. For the 50th game, the NFL announced on 4 June 2014 that it would be Super Bowl 50, not Super Bowl L.

Its creative director, Shandon Melvin, said the lone L was hard to design around. Unlike the other numerals it's lopsided, and on its own it could read as the "loser" hand gesture. The league drew 73 mock-ups with either L or 50 before deciding.

The numerals came back the next year, for Super Bowl LI.

Questions

What is 2026 in Roman numerals?

MMXXVI: two thousands, two tens, a five and a one.

Why is 4 written IV and not IIII?

The standard rules subtract when a smaller numeral comes before a larger one, and never repeat a letter four times. Some clock faces still use IIII, but it isn't the standard form.

What is the largest Roman numeral?

3999, MMMCMXCIX, in the standard system. Larger numbers used a bar over a numeral to multiply it by 1000, which this converter doesn't write.

Is there a Roman numeral for zero?

No. The system has no zero, so 0 is left as it is and noted under the output.