You see them on clock faces, book chapters, the Super Bowl and the copyright line at the end of films. Roman numerals look mysterious but run on just seven letters and one rule. Once you know them, you can read any number up to 3999.
The hardest common case, checked. Type
1994into our Roman numeral converter and it returns MCMXCIV. That one number exercises subtractive notation three times over — CM for 900, XC for 90, IV for 4 — which is exactly where hand conversion goes wrong (MCMXCIIII and MDCCCCLXXXXIV are both wrong, and both get written). The conversion runs in your browser, so you can check any year in the box above without sending it anywhere.
The seven letters
| Letter | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Numbers are built by writing letters from largest to smallest and adding them up: MDCLXVI = 1000 + 500 + 100 + 50 + 10 + 5 + 1 = 1666.
The one rule: subtractive notation
To avoid four identical letters in a row, a smaller letter placed before a larger one is subtracted:
- IV = 5 − 1 = 4 (not IIII)
- IX = 9
- XL = 40, XC = 90
- CD = 400, CM = 900
So 1994 = MCMXCIV: M (1000) + CM (900) + XC (90) + IV (4). Reading it is just chunking it into these pieces.
Why there’s no zero (and no big numbers)
The Roman system has no symbol for zero and no place value, which makes arithmetic awkward — one reason it lost out to the Arabic numerals we use today. Standard notation also stops at 3999 (MMMCMXCIX); going higher needs a bar over letters to mean “×1000”, which isn’t part of everyday usage.
The upper bound is not a stylistic preference — it is enforced. Type 4000 into our converter and the output field stays empty and it says ✗ Enter an integer from 1 to 3999 instead. The reason is arithmetic: M is the largest letter there is, and there is no letter for 5000 to subtract from, so 4000 would have to be written MMMM — four identical letters, which is exactly what the subtractive rule exists to avoid. Larger numbers need the medieval vinculum (a bar meaning ×1000), which is not the notation you see in film credits.
Read the year on any film
Copyright years are the most common place people meet Roman numerals in the wild. MMXXVI = 2026: MM (2000) + XX (20) + VI (6). Paste it into the Roman numeral converter and it decodes instantly — and it works the other way too, turning any number 1–3999 into its numeral.
A quick conversion chart
Break any number into thousands, hundreds, tens and units, then read the columns left to right:
| Units | Tens | Hundreds | Thousands |
|---|---|---|---|
| I = 1 | X = 10 | C = 100 | M = 1000 |
| II = 2 | XX = 20 | CC = 200 | MM = 2000 |
| III = 3 | XXX = 30 | CCC = 300 | MMM = 3000 |
| IV = 4 | XL = 40 | CD = 400 | |
| V = 5 | L = 50 | D = 500 | |
| VI = 6 | LX = 60 | DC = 600 | |
| VII = 7 | LXX = 70 | DCC = 700 | |
| VIII = 8 | LXXX = 80 | DCCC = 800 | |
| IX = 9 | XC = 90 | CM = 900 |
For example 2024 = MM + XX + IV = MMXXIV, and 348 = CCC + XL + VIII = CCCXLVIII.
Rather than reprint a letter table, here is what our own Roman numeral converter actually returned. The first six rows cover five of the six subtractive pairs; CM only appears once you pass 900, which is why MCMXC looks so dense for a year as recent as 1990.
| Number | Our converter’s output |
|---|---|
4 | IV |
9 | IX |
14 | XIV |
40 | XL |
90 | XC |
400 | CD |
1990 | MCMXC |
2026 | MMXXVI |
3999 | MMMCMXCIX |
Common mistakes
- Writing 4 as IIII. The correct form is IV. Clock faces are the famous exception — many still use IIII for visual balance, a tradition rather than a rule.
- Repeating a letter four times. I, X, C and M may repeat at most three times in a row, so 40 is XL, not XXXX.
- Repeating V, L or D. There is no VV, LL or DD — you move up to the next symbol instead.
- Over-subtracting. Only certain pairs are allowed. 49 is XLIX, not IL; 99 is XCIX, not IC; 999 is CMXCIX, not IM. Subtraction uses only I, X and C, and each only before the next two larger symbols.
Years worth recognising
- MDCCLXXVI = 1776 — M (1000) + DCC (700) + LXX (70) + VI (6).
- MCMLXXXIV = 1984 — M (1000) + CM (900) + LXXX (80) + IV (4).
- MMXXVI = 2026 — the current copyright year.
If a numeral runs longer than a few letters, converting it by hand is slow and error-prone. The Roman numeral converter decodes it instantly and shows the breakdown, so you can check the logic yourself.
FAQ
What is the largest Roman numeral?
In standard notation, 3999 (MMMCMXCIX). Larger values historically took a bar over a letter (a vinculum) to multiply it by 1000, but that is rarely seen today.
Is there a Roman numeral for zero?
No. The system has no symbol for zero and no place value; the concept simply was not part of it. Medieval scholars occasionally wrote the Latin word nulla (“none”) when they needed to express it.
Related tools
- Converting between binary, decimal and hex? Use the number base converter.