Roman Numeral Converter
Convert numbers and dates to Roman numerals and back, with a step-by-step breakdown.
MCMXCIV
MCMXCIV = M 1,000 + CM 900 + XC 90 + IV 4
Converts whole numbers to Roman numerals and Roman numerals back to numbers, and writes a date in Roman numerals in the order and style you choose. Every result is broken down place by place, and a numeral that is not in standard form gets an explanation of the rule it breaks rather than a bare rejection.
How to use it
In Number mode, type into either field: a number in Number fills in the Roman numeral, and a numeral fills in the number. Numerals may be typed in any case, with spaces. The standard range is 1 to 3,999; Large numbers extends it to 3,999,999 with overlined letters.
In Date mode, pick a date and choose:
- Order — day, month, year (the default); month, day, year; or year, month, day.
- Separator — a middle dot (the default), a full stop, a hyphen, a slash or a space.
- Year — in full, or its last two digits, written as they stand: 2026 becomes XXVI. A year ending in 00 has no two-digit numeral, since there is no Roman zero.
Years after 3999 need Large numbers. The address bar keeps what you typed and the options, so a copied link opens the same conversion. Everything runs in your browser.
How Roman numerals are written
Seven letters carry the values: I 1, V 5, X 10, L 50, C 100, D 500 and M 1,000. Letters run from largest to smallest and add up. A smaller letter placed before a larger one is subtracted, but only in six pairs: I before V and X, X before L and C, and C before D and M. V, L and D are never repeated or subtracted, and no letter appears more than three times in a row.
Each decimal place is written on its own, which is how the tool breaks a numeral down: MCMXCIV is M 1,000 + CM 900 + XC 90 + IV 4. The largest standard numeral is MMMCMXCIX, 3,999.
Larger numbers use the vinculum, a bar over a letter that multiplies it by 1,000. Above 3,999 the tool overlines the whole thousands part, so 4,000 is I̅V̅ and 3,999,999 is M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX. The bar is a combining character, and some fonts place it unevenly.
A numeral is accepted only in the standard form the tool would write for its value. Anything else is explained: for IC the message reads “IC is not standard: I comes only before V or X”, and for VV “VV is not standard: V is used only once; 10 is X”. Where the letters only add up, as in VV, the message names the standard form; where a subtraction is misused, as in IC, it names the rule, since the intended number is not certain.
Examples
A year
1994 is MCMXCIV: M 1,000 + CM 900 + XC 90 + IV 4.
A wedding date
21 June 2025, day first with middle dots, is XXI · VI · MMXXV.
A numeral read back
MMXXVI is 2026: MM 2,000 + XX 20 + VI 6.
Roman numerals reference
| Number | Numeral | Number | Numeral |
|---|---|---|---|
| 1 | I | 11 | XI |
| 2 | II | 12 | XII |
| 3 | III | 13 | XIII |
| 4 | IV | 14 | XIV |
| 5 | V | 15 | XV |
| 6 | VI | 16 | XVI |
| 7 | VII | 17 | XVII |
| 8 | VIII | 18 | XVIII |
| 9 | IX | 19 | XIX |
| 10 | X | 20 | XX |
| Tens | Numeral | Hundreds | Numeral | Thousands | Numeral |
|---|---|---|---|---|---|
| 10 | X | 100 | C | 1,000 | M |
| 20 | XX | 200 | CC | 2,000 | MM |
| 30 | XXX | 300 | CCC | 3,000 | MMM |
| 40 | XL | 400 | CD | ||
| 50 | L | 500 | D | ||
| 60 | LX | 600 | DC | ||
| 70 | LXX | 700 | DCC | ||
| 80 | LXXX | 800 | DCCC | ||
| 90 | XC | 900 | CM |
Conventions and sources
No standards body defines Roman numerals. The tool follows the subtractive form in general use today, with the vinculum for thousands. The Super Bowl numbering below is the NFL’s own.
Sources
- NFL to take one-year hiatus from Roman numerals for Super Bowl 50 — ESPN
- Super Bowl LX: Why Does the Super Bowl Use Roman Numerals? — NBC
- Roman IIII vs. IV on clock dials — Electric Time Company
Reviewed
Frequently asked questions
See also
- Number to Words Converter — to write a number in words, as on a cheque.
- Number Base Converter — for binary, octal and hexadecimal.