How to use it
- Choose the Conversion: a number, Roman numerals or a date.
- Type the number, the Roman numerals or the date in the box that appears.
- Read the Result. For Roman numerals, check Standard form? to see whether the letters are the usual form.
- Go through How it is worked out to see which parts make up the number.
The rules of Roman numerals
The symbols I, V, X, L, C, D and M stand for 1, 5, 10, 50, 100, 500 and 1000. Symbols are added from left to right, except that a smaller symbol before a larger one is subtracted. Subtraction is used only in the pairs IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
A symbol is not repeated more than three times in a row, so 4 is IV and not IIII, and 9 is IX and not VIIII. Every number from 1 to 3999 has one standard form, which is what this tool writes.
1994 = 1000 + 900 + 90 + 4 = M + CM + XC + IV = MCMXCIVDates in Roman numerals
A date written as day, month and year, separated by full stops, is a common form for inscriptions, plaques and tattoos. Each part is written as its own Roman numeral: the day 10 is X, the month 11 is XI and the year 2026 is MMXXVI, so 10 November 2026 is X.XI.MMXXVI.
The tool uses the year as a number from 1 to 3999. The day and month are written in the same way as any number.
What the calculator does not cover
- Numbers above 3999. Larger numbers have no standard form in this system, and bars or other marks are not used here.
- Negative numbers, zero and fractions. Roman numerals have no way to write them.
- Historical variants, such as IIII on clock faces or the older forms with other symbols.
Worked example: 1994 and the date 10 November 2026
1994 is 1000 + 900 + 90 + 4, which is M + CM + XC + IV, so it is written MCMXCIV. Each subtractive pair, CM, XC and IV, is one of the allowed pairs.
The date 10 November 2026 is written with each part on its own: 10 is X, 11 is XI and 2026 is MMXXVI, so the result is X.XI.MMXXVI.
| Result | |
|---|---|
| 1994 in Roman numerals | MCMXCIV |
| 10 November 2026 | X.XI.MMXXVI |
| IIII read as a number | 4, not standard: IV is the standard form |
Frequently asked questions
Why is 4 written IV and not IIII?
The standard form subtracts 1 from 5 for 4, and subtracts 1 from 10 for 9. Writing IIII is an older habit that is still seen on some clock faces, but the standard form of 4 is IV, and the tool marks IIII as not standard.
What is the largest number I can write in Roman numerals?
The standard form goes up to 3999, which is MMMCMXCIX. Larger numbers need extra symbols that are not part of the standard system, so the tool does not convert them.
How do I write a date in Roman numerals?
Choose Date to Roman numerals and pick the date. The day, the month and the year are each converted, and the parts are joined with full stops. 10 November 2026 is X.XI.MMXXVI.
Is XXXX a standard Roman numeral?
No. A symbol is not repeated more than three times in a row, so 40 is written XL. The tool reports XXXX as a non-standard form and gives its standard form.
Can I type the letters in lower case?
Yes. The letters are read in either case, so mcmxciv gives the same result as MCMXCIV.
Are the numbers and letters I type sent to a server?
No. The conversion runs in your browser, and nothing you type is sent to us.
Sources
Figures and text last checked on Tuesday, November 10, 2026.