The seven letters
Roman numerals use seven letters, each with a fixed value. There is no zero and no letter for any other value; everything is built from these seven by adding and, in six special cases, subtracting.
| Letter | Value | Memory aid |
|---|---|---|
| I | 1 | one finger |
| V | 5 | an open hand |
| X | 10 | two hands |
| L | 50 | |
| C | 100 | centum, Latin for hundred |
| D | 500 | half of an old symbol for 1,000 |
| M | 1,000 | mille, Latin for thousand |
Adding and the subtraction rule
Letters are written from the largest value to the smallest and added: VIII is 5 + 1 + 1 + 1 = 8, LXXII is 50 + 10 + 10 + 1 + 1 = 72, MDCLXVI is 1,666. The same letter may appear up to three times in a row, so 3 is III and 30 is XXX.
For 4 and 9 at each place, a smaller letter is put before a larger one and subtracted. Only six such pairs exist: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900. I can only stand before V and X, X only before L and C, and C only before D and M. V, L and D never stand before a larger letter and are never repeated. This is why 49 is XLIX and not IL, and 99 is XCIX and not IC.
Try it here: Roman Numeral Converter
Open the full tool pageA quick method for any number
Split the number into its places and write each place separately, then join them. Every place uses the same pattern of nine forms, only with different letters.
| Digit | Units | Tens | Hundreds | Thousands |
|---|---|---|---|---|
| 1 | I | X | C | M |
| 2 | II | XX | CC | MM |
| 3 | III | XXX | CCC | MMM |
| 4 | IV | XL | CD | |
| 5 | V | L | D | |
| 6 | VI | LX | DC | |
| 7 | VII | LXX | DCC | |
| 8 | VIII | LXXX | DCCC | |
| 9 | IX | XC | CM |
Reading years
Years are the most common Roman numerals today: film credits, building inscriptions, book title pages and sports events. Read them by finding the place boundaries. MCMXCIV splits into M, CM, XC and IV: 1,000 + 900 + 90 + 4 = 1994. MMXXVI splits into MM, XX and VI: 2026. MDCCLXXVI splits into M, DCC, LXX and VI: 1776.
A useful habit is to look for the pairs first. Whenever a letter is followed by a larger one, those two letters belong together and are subtracted; everything else is added. With practice you see CM, XC and IV as single blocks.
- MCMLXXXIV = 1984
- MCMXCIX = 1999
- MM = 2000
- MMXXIV = 2024
- MMXXV = 2025
Writing dates for tattoos and engravings
For a date, convert the day, the month and the year separately and join them with a separator such as a dot or a middle dot. 14 February 2024 becomes XIV.II.MMXXIV in day-month-year order and II.XIV.MMXXIV in the American month-day-year order. Decide which order the reader expects, because 07.04 can mean two different days.
A two-digit year is shorter (XXIV) but fails for 2000, because 00 has no Roman numeral. Before you engrave or tattoo a date, paste each part back into the converter to check it, and ask for a clear serif font so that I, l and V cannot be confused.
Roman numerals also appear in the names of monarchs and popes (Elizabeth II, Louis XIV), in the numbering of sequels and major events, and in the outlines of legal documents, where lowercase numerals such as i, ii and iii number clauses. The same rules apply everywhere, so once you can read a year you can read them all.
Large numbers and the overline
The standard system ends at 3,999 (MMMCMXCIX), because writing MMMM would break the three-in-a-row rule. For larger numbers the Romans drew a bar over a numeral to multiply it by 1,000: V with a bar is 5,000, X with a bar 10,000, M with a bar one million. This is called a vinculum. In digital text the bar is a combining overline character, which most apps show, though its position depends on the font.
Common mistakes
- IIII for 4: seen on clock faces, but IV is standard in writing.
- VV, LL or DD: these letters are never repeated; use X, C and M.
- IC for 99 or IL for 49: I can only be subtracted from V and X. Write XCIX and XLIX.
- IIX for 8: only one letter can be subtracted. Write VIII.
- Looking for a zero: empty places are simply left out, so 2000 is MM and 2005 is MMV.