Converter and table, 1 to 3999
Roman numerals converter
Convert roman numerals both ways, from 1 to 3999, and see the rule that writes MCMXCIVfor 1994.
How to use it
Type a number from 1 to 3999 into the left box. The roman numeral appears on the right as you type.
Paste a roman numeral into the right box to go the other way. Upper and lower case are the same.
Several numbers separated by spaces convert at once, in order, which is handy for checking a list of dates or chapters.
The rule in one sentence
Seven symbols stand for one, five, ten, fifty, a hundred, five hundred and a thousand. A number is written from the largest value to the smallest, adding the symbols up, with one exception: when a smaller symbol comes before a larger one, it is subtracted. That exception happens in only six pairs, and it is the one thing that makes roman numerals hard to read at a glance. Three is III, three strokes added. Four would be four strokes, but the rule prefers IV, one before five. Eight adds again: VIII. Nine subtracts again: IX.
The converter applies exactly that. It walks the list of thirteen values in the table below, largest first, and for each writes the symbol as many times as it fits into what remains of the number. Because the six subtractive pairs sit in the list as values of their own, four hundred comes out asCD with no special case in the program. Nineteen ninety-four comes out asMCMXCIV, which is a thousand, plus nine hundred, plus ninety, plus four, and reads back as1994.
In the other direction the converter reads the symbols left to right, adds the values, then writes the result out again. If the spelling does not match what you pasted, the numeral was not the standard form of that number, and the tool refuses it instead of guessing. That is what happens with four strokes, with a one before a thousand, and with any symbol repeated four times.
Table
The thirteen values that generate every numeral up to 3999: the seven symbols and the six subtractive pairs. To write any number, walk this table top to bottom.
| Value | Numeral |
|---|---|
| Symbols | |
| 1000 | M |
| 500 | D |
| 100 | C |
| 50 | L |
| 10 | X |
| 5 | V |
| 1 | I |
| Subtractive pairs | |
| 900 | CM |
| 400 | CD |
| 90 | XC |
| 40 | XL |
| 9 | IX |
| 4 | IV |
Years, centuries and clocks
Centuries are the commonest use today, and the easiest, because the number is small: the eighteenth century is XVIII, the twenty-first XXI. Full years get long, and that is why the credits of an old film take a moment to read: MCMXCIV spends seven symbols on a four-digit number. Fifty is one symbol, L, and forty-nine, which looks as if it should need many, ends up as XLIX, two subtractions in a row. Eighty-eight is the longest number under a hundred, LXXXVIII.
The Romans themselves did not follow the subtractive rule strictly, and ancient inscriptions show four as four strokes and nine spelled in other ways. The rule the converter uses is the one that settled in the Middle Ages and is taught today, and it is the only one with a single spelling for each number, which is what a converter needs. Where a convention diverges on purpose, as on clock faces, the page says so instead of accepting both forms.
Frequently asked
How do you write the current year in roman numerals?
Two thousand and twenty-six is MMXXVI: two thousands, two tens, and a five followed by a one. The twenty-first century is XXI, which is how it appears on facades and in film credits.
Why is four IV and not IIII?
By the subtractive rule: a smaller symbol placed before a larger one is subtracted from it. Four is IV, nine is IX, forty is XL, ninety is XC, four hundred is CD and nine hundred is CM. Those six pairs are the whole exception. Old clock faces often use four strokes for four; that is a clockmakers' convention, and the converter refuses the four-stroke form instead of guessing.
What is the largest roman numeral?
In the standard form, with the seven symbols and no bars, the largest is 3999, written MMMCMXCIX. Above that the M would have to repeat four times, which the rule forbids. The notation with a bar over a symbol, multiplying it by a thousand, exists but the converter does not use it.
Why does the converter refuse some numerals?
Because every number has one standard spelling, and a converter that accepts more than one cannot say which is right. XIV is fourteen, but the same idea written with a one before a fifteen is no numeral at all. The converter reads what you pasted, writes the number back, and accepts it only if the two spellings match.
Where are roman numerals still used?
In centuries and millennia, in the names of kings and popes, in film and television credits, on clock faces, in book chapters, and in the numbering of recurring events, such as a festival whose fifty-eighth edition is LVIII. In almost all of these the number stays below a hundred, the range in which reading is still quick.