Convert any number from 1 to 3,999 to Roman numerals, or a Roman numeral back to a number — with a clear explanation when something isn’t valid.
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
Written and reviewed by Mohsin Iqbal · Last reviewed August 2026
| Symbol | Value | Symbol | Value |
|---|---|---|---|
| I | 1 | L | 50 |
| V | 5 | C | 100 |
| X | 10 | D | 500 |
| M | 1000 | ||
Every Roman numeral is built from just these seven letters, combined by two rules: addition, where symbols are written largest to smallest and their values summed, and subtraction, used only in six specific pairs to keep certain numbers short.
Break the number into thousands, hundreds, tens and ones, and convert each piece separately using the rules above.
| Step | Working | Result |
|---|---|---|
| Take 1,994 | 1000 + 900 + 90 + 4 | — |
| Thousands | 1000 | M |
| Hundreds | 900 (the CM pair) | CM |
| Tens | 90 (the XC pair) | XC |
| Ones | 4 (the IV pair) | IV |
| Combine | M + CM + XC + IV | MCMXCIV |
The same method, run in reverse, converts a Roman numeral back to a number: split it into the same four groups, and add their values.
| Number | Roman | Number | Roman | Number | Roman |
|---|---|---|---|---|---|
| 1 | I | 11 | XI | 90 | XC |
| 2 | II | 14 | XIV | 100 | C |
| 3 | III | 19 | XIX | 400 | CD |
| 4 | IV | 20 | XX | 500 | D |
| 5 | V | 40 | XL | 900 | CM |
| 9 | IX | 50 | L | 1000 | M |
| 10 | X | 2026 | MMXXVI | 3999 | MMMCMXCIX |
With the seven standard symbols, the largest number expressible is 3,999 — MMMCMXCIX. Four thousand would need a symbol between M (1,000) and the never-repeated V-bar convention, and that's where the trail runs out: historically, Romans marked larger numbers with a vinculum, a bar drawn over a letter that multiplied its value by 1,000. Under that convention, a barred V meant 5,000 and a barred M meant 1,000,000.
The catch is that the vinculum was never standardised into one fixed system. Different classical sources used it differently, and no single modern authority defines a canonical way to write, say, 47,000 in Roman numerals. Rather than invent one answer among several defensible options, this calculator sticks to the range that actually has a single agreed standard: 1 to 3,999. In practice this covers essentially every real use — dates, clock faces, book chapters, sequel numbering — since none of them reach into the thousands range where the ambiguity starts.
There is no Roman numeral for zero. The concept of zero as a number wasn't part of the Roman counting system at all — where a value of nothing needed naming, Latin used the word nulla, not a symbol. This is one of the reasons the Hindu-Arabic system, with its positional zero, eventually replaced Roman numerals for arithmetic: without zero, calculations like long division are far more cumbersome.
| Context | Example |
|---|---|
| Clock faces | Many analogue clocks and watches |
| Monarchs and popes | Elizabeth II, Pope John Paul II |
| Sequels and editions | Rocky IV, Super Bowl LVIII |
| Book and document structure | Chapter numbers, front-matter page numbers |
| Building cornerstones | Construction year, MCMXXII |
| Outlines | Major section headings (I, II, III) |
One quirk worth knowing: clock faces conventionally use IIII rather than IV for four o'clock, breaking the standard subtractive rule. The reasons offered range from visual balance opposite VIII to tradition — it's a design convention on timepieces specifically, not evidence that IIII is valid Roman numeral notation generally.
A number written using letters from the Latin alphabet — I, V, X, L, C, D and M — rather than the digits 0 to 9. Values are built by adding and, in six specific cases, subtracting these symbols according to fixed rules.
Split the number into thousands, hundreds, tens and ones, then convert each part using the standard symbols and the six subtractive pairs (IV, IX, XL, XC, CD, CM) where needed. Combine the parts from largest to smallest. For example, 1994 becomes M (1000) + CM (900) + XC (90) + IV (4) = MCMXCIV.
Read left to right, adding each symbol's value — except when a smaller symbol appears directly before a larger one, which means subtract the smaller value instead. MCMXCIV becomes M (1000) + CM (900) + XC (90) + IV (4) = 1994.
I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). Every standard Roman numeral from 1 to 3,999 is built from combinations of just these seven letters.
Writing IIII would repeat I four times, which standard Roman numeral rules don't allow — a symbol may repeat at most three times. IV uses the subtractive rule instead: I placed before V means 5 minus 1, giving 4 in two characters rather than four.
The same subtractive principle as IV: I before X means 10 minus 1. Writing VIIII (5+4) would use five characters and repeat I four times, both of which break the standard rules.
Using the standard seven symbols, the largest representable number is 3,999, written MMMCMXCIX. Numbers above that historically used a vinculum — an overline meaning multiply by 1,000 — but that convention was never standardised into a single agreed system.
No. The Roman numeral system has no symbol for zero at all — the concept simply wasn't part of it. Where zero needed expressing in Latin, the word "nulla" was used instead of a numeral.
Clock faces, the regnal numbers of monarchs and popes, sequels and editions (Super Bowl LVIII, Rocky IV), chapter numbers and front-matter page numbers in books, building cornerstones, and outline headings are all still common.
Two principles: addition, where symbols are written largest to smallest and summed, and subtraction, used only for six specific pairs — IV, IX, XL, XC, CD and CM — where a smaller symbol precedes a larger one. I, X, C and M may repeat up to three times; V, L and D never repeat.
Clock and watch faces conventionally use IIII for four o'clock, which breaks the standard subtractive rule. It's a specific design tradition on timepieces — reasons range from visual symmetry with VIII to simple convention — not a sign that IIII is valid Roman numeral notation more generally.
No. I can only be subtracted from V or X, never from C. The correct form of 99 is XCIX — XC (90) plus IX (9). IC looks logical but isn't a legal subtractive pair under the standard rules.