Roman Numeral Converter

2026 is MMXXVI, and MCMXCIX is 1999

Roman numerals use seven letters: I (1), V (5), X (10), L (50), C (100), D (500) and M (1,000). You write them from largest to smallest and add them up. The one twist is that 4 and 9 are written by putting a smaller letter in front of a larger one, which subtracts it, so that no letter has to repeat four times. That is why 4 is IV and 9 is IX.

To write 2026, split it into 2,000 + 20 + 6, which is MM + XX + VI = MMXXVI. To read MCMXCIX, cut it into M (1,000) + CM (900) + XC (90) + IX (9) and you get 1999. The converter above fills in the other box whichever one you type in, and it also tells you whether the numeral you entered is standard, an old additive form such as the IIII on clock faces, or something that breaks the rules like MIM.

When you need to convert or check a Roman numeral

Roman numerals still turn up wherever something is meant to look formal or lasting. Since many of those places are hard to correct later, it is worth confirming that what you wrote is the standard form.

• Dates for a ring, a tattoo or a plaque: an anniversary is often engraved as a Roman numeral date. Type 12.25.2024 in the number box and you get XII.XXV.MMXXIV, with the separators left as they were.
• Copyright years in film and TV credits: the end credits often print the year as MCMXCIV or MMXXV. Paste it into the Roman numeral box and the year appears.
• Front matter and outlines: the preface of a book is usually paged i, ii, iii in lowercase, and report outlines often use I, II, III for main sections. The forms card lets you copy the style you need.
• Monarchs, popes and sporting events: Elizabeth II, Louis XIV and Pope John Paul II all carry Roman numerals, and so does the Super Bowl. The game played on February 8, 2026 was Super Bowl LX, though the NFL branded the 2016 game Super Bowl 50 rather than Super Bowl L.
• Clock faces: many Roman numeral clocks show four o'clock as IIII instead of IV. That is an old additive form rather than a mistake, and the section on IIII explains it.

How to use it

1. Type a number in the number box and the Roman numeral box fills in at once. If you type several numbers separated by dots, slashes or hyphens, such as 10.22.2026 or 12/25/2024, each one is converted on its own and your separators stay put. The "Today's date" button enters today's date in month-day-year order.
2. The Roman numeral box accepts upper or lower case, and single-character symbols such as Ⅻ. You can also use the I to M buttons on the keypad. For an overlined letter (x1,000), turn on the overline button and press the letter, or type an underscore before it on a keyboard, as in _V.
3. The badge at the top of the breakdown is the verdict. If it does not say "Standard", you get the reason and the standard form, and "Use standard form" rewrites the box for you. The large tiles show the letters for each place and what each is worth.
4. On the place-value board, tapping a cell changes the digit in that place and leaves the others alone. The arrow keys move between cells, and "Ten thousands and up" opens the rows for 10,000s, 100,000s and millions.
5. The forms card copies the standard form, lowercase, single-character symbols (1 to 12), the additive form and the underscore form one at a time. "Copy link" copies a link that reopens the current conversion.

Seven letters and three rules

Only seven letters are used, and of these only I, X and C can stand in front of a larger letter to subtract.

1. Write from largest to smallest and add. VI = 5 + 1 = 6, LX = 50 + 10 = 60, MDC = 1,000 + 500 + 100 = 1,600.
2. A smaller letter directly before a larger one is subtracted. Only I, X or C can do this, and only before a letter worth five or ten times as much. That leaves exactly six subtractive pairs: IV, IX, XL, XC, CD and CM. It is why 99 is XC + IX = XCIX and never IC.
3. I, X, C and M repeat at most three times, and V, L and D never repeat. Write 4 as IV rather than IIII, and 10 as X rather than VV.

Look up each place and join the pieces

You do not have to work through the rules one by one. Split the number into thousands, hundreds, tens and ones, find the matching letters for each place in the table below, and join them from left to right. A place with a zero contributes nothing.

• 1994 = 1,000 + 900 + 90 + 4 → M + CM + XC + IV = MCMXCIV
• 2006 = 2,000 + 6 → MM + VI = MMVI (the empty hundreds and tens are simply skipped)
• 3888 = 3,000 + 800 + 80 + 8 → MMM + DCCC + LXXX + VIII = MMMDCCCLXXXVIII (15 letters, the longest numeral up to 3,999)

In the thousands column, 4 to 9 move to overlined letters because M cannot be written four or more times in a row. See the section on 4,000 and above.

1 to 100, and the years people look up

Here are 1 to 100, which is handy for numbered lists and chapter headings. Anything else can go into the converter above.

1. 1I
2. 2II
3. 3III
4. 4IV
5. 5V
6. 6VI
7. 7VII
8. 8VIII
9. 9IX
10. 10X
11. 11XI
12. 12XII
13. 13XIII
14. 14XIV
15. 15XV
16. 16XVI
17. 17XVII
18. 18XVIII
19. 19XIX
20. 20XX
21. 21XXI
22. 22XXII
23. 23XXIII
24. 24XXIV
25. 25XXV
26. 26XXVI
27. 27XXVII
28. 28XXVIII
29. 29XXIX
30. 30XXX
31. 31XXXI
32. 32XXXII
33. 33XXXIII
34. 34XXXIV
35. 35XXXV
36. 36XXXVI
37. 37XXXVII
38. 38XXXVIII
39. 39XXXIX
40. 40XL
41. 41XLI
42. 42XLII
43. 43XLIII
44. 44XLIV
45. 45XLV
46. 46XLVI
47. 47XLVII
48. 48XLVIII
49. 49XLIX
50. 50L
51. 51LI
52. 52LII
53. 53LIII
54. 54LIV
55. 55LV
56. 56LVI
57. 57LVII
58. 58LVIII
59. 59LIX
60. 60LX
61. 61LXI
62. 62LXII
63. 63LXIII
64. 64LXIV
65. 65LXV
66. 66LXVI
67. 67LXVII
68. 68LXVIII
69. 69LXIX
70. 70LXX
71. 71LXXI
72. 72LXXII
73. 73LXXIII
74. 74LXXIV
75. 75LXXV
76. 76LXXVI
77. 77LXXVII
78. 78LXXVIII
79. 79LXXIX
80. 80LXXX
81. 81LXXXI
82. 82LXXXII
83. 83LXXXIII
84. 84LXXXIV
85. 85LXXXV
86. 86LXXXVI
87. 87LXXXVII
88. 88LXXXVIII
89. 89LXXXIX
90. 90XC
91. 91XCI
92. 92XCII
93. 93XCIII
94. 94XCIV
95. 95XCV
96. 96XCVI
97. 97XCVII
98. 98XCVIII
99. 99XCIX
100. 100C

From 4,000 up, write an overline (vinculum)

With the standard rules alone, MMMCMXCIX (3,999) is the largest number, because M may not be written four times. For bigger numbers a bar is drawn over the letters to multiply them by 1,000. The bar is called a vinculum. Wikipedia's article on Roman numerals gives IV̅ = 4,000 and XXV̅ = 25,000 as examples.

For anything from 4,000 up, this converter writes the whole thousands part as a Roman numeral with an overline over every letter and then adds the last three digits in ordinary letters. That reaches 3,999,999 = M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX.

Other ways of writing the same number

Large numbers are not written the same way everywhere. This converter also reads forms that use M for the thousand instead of I̅, such as MV̅ for 4,000, V̅M for 6,000 and X̅MMM for 13,000; the value is the same, so it labels them "Variant". MMMM for 4,000 is read as "Old additive". In every case the converter shows its own form beside the input.

Typing an overlined letter

An overline is made by adding the combining character U+0305 (COMBINING OVERLINE) after the letter, as in X̅. If that is awkward on your keyboard, turn on the overline button on the keypad or put an underscore before the letter, as in _X. CalculatorSoup's converter also accepts a leading underscore. Fonts differ, so the line may look detached from the letter or run into the next one; check the result in the real font before you print or engrave anything. Wikipedia notes that a three-sided box multiplies by 100,000, but this converter does not use that notation and stops at 3,999,999.

IIII on clock faces and other additive forms

Writing 4 as IIII instead of IV is not so much an error as an older additive style. Wikipedia says that modern clock faces using Roman numerals still very often use IIII for four o'clock but IX for nine o'clock, a practice that goes back to very early clocks such as the Wells Cathedral clock of the late 14th century.

In Roman times 4, 40 and 400 were often written additively as IIII, XXXX and CCCC; the additive forms for 9, 90 and 900 (VIIII, LXXXX and DCCCC) appear less often. The two conventions could be mixed in one numeral: the numbered gates of the Colosseum use IIII systematically instead of IV but write 40 as XL, so gate 44 is labelled XLIIII. Officers of the Legio XVIII wrote the number as XIIX. This converter reads additive forms and shows their value as "Old additive", but it will not give a value for something like XIIX, where two subtracting letters collide, because there is no single way to read it.

Typing Roman numerals in documents

Unicode contains single-character symbols Ⅰ (U+2160) to Ⅻ (U+216B), plus Ⅼ, Ⅽ, Ⅾ and Ⅿ, and lowercase ⅰ (U+2170) to ⅻ (U+217B) with ⅼ, ⅽ, ⅾ and ⅿ. The Unicode Standard says these were encoded for compatibility with East Asian standards and that for most purposes it is preferable to compose Roman numerals from the appropriate Latin letters. Searching a document for XII, for example, will not find a Ⅻ.

In Word, Microsoft's support page for Latin-based symbols explains a general method: type the Unicode code of a character, then press Alt+X to turn it into the character. If Alt+X converts the wrong digits, put the prefix U+ in front of the code. The page also warns that some Office programs, PowerPoint among them, cannot convert codes this way. The code for the overline is 0305, but whether it attaches neatly to the letter before it depends on the program and font, so the copy buttons in the converter, which carry the overline with the letters, are usually the easier route.

Common mistakes

These are forms that often show up on tattoo mock-ups and hand-made tables. Press "Try it" and the converter above judges that form.

Some people also write 0 as O or N, or try to fill the empty place in a number like 2006 with something. There is no Roman numeral for zero, so an empty place is simply left out.

Limits and caveats

• Only whole numbers from 1 to 3,999,999 are converted. Zero, negative numbers and decimals are not. The Romans wrote one half as S (semis) and one twelfth as a single dot (uncia), but this converter does not handle fractions.
• Apostrophus forms such as CIↃ (1,000) and IↃ (500), older letters such as ↀ, and the three-sided box for 100,000 are not read.
• Forms like IIX and XIIX, where two or more subtracting letters stand before a larger one, have no single reading, so no value is given.
• There are several conventions for 4,000 and above. This converter overlines the whole thousands part, so check which convention the person or publisher receiving your numeral expects.
• When you convert a date in parts, the order is whatever you typed. Decide first whether you mean month-day-year, as in the United States, or day-month-year, as in the United Kingdom and many other countries.
• The overline is a combining character and can sit in slightly the wrong place in some fonts and programs. Check a proof before you hand text over for engraving or printing.

Sources

• 01Wikipedia: Roman numeralsVinculum IV̅ = 4,000 and XXV̅ = 25,000, the three-sided box x100,000, clock faces with IIII and the Wells Cathedral clock, Colosseum gate XLIIII, Legio XVIII XIIX, N for zero about 725, S and uncia, apostrophus
• 02The Unicode Standard, Chapter 22: SymbolsRoman numerals in Number Forms (U+2150 to U+218F) are compatibility characters; composing them from Latin letters is usually better
• 03Microsoft Support: Insert ASCII or Unicode Latin-based symbolsType the Unicode code, then press Alt+X; the U+ prefix; not every Office program supports it
• 04Wikipedia: Date format by countryThe United States uses month-day-year; the United Kingdom and many other countries use day-month-year
• 05Wikipedia: Super Bowl LXPlayed on February 8, 2026 at Levi's Stadium, Santa Clara
• 06Wikipedia: Super Bowl 50The 2016 game was branded with the Arabic numeral 50 instead of L
• 07CalculatorSoup: Roman Numeral ConverterRange 1 to 3,999,999; a leading underscore marks a letter with an overline

Sources checked on 2026-10-22.

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