Roman Numerals Converter
This Roman numerals converter goes both ways: type a number to get the numerals, or type numerals to get the number. It works from 1 to 3999, detects which way you're converting, and shows a breakdown of how the symbols add up. It also validates the numerals, so an invalid string gets flagged rather than guessed. It's free and accurate, you won't need an account, and it's great for dates, tattoos, chapter numbers, and decoding movie years. You'll see the result the moment you type.
- Both directions
- Auto-detects
- 1 to 3999
- Breakdown
- Full chart
Last updated June 17, 2026 Standard numerals, 1 to 3999 Reviewed by the Calcowa team
Type a whole number from 1 to 3999, or Roman numerals using I, V, X, L, C, D, and M. The tool detects which way to convert.
How do Roman numerals work?
Roman numerals build numbers from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. You add symbols from largest to smallest, so MMXV is 1000 plus 1000 plus 10 plus 5, or 2015. The clever part is subtraction: when a smaller symbol sits just before a larger one, you subtract it, which is how 4 becomes IV and 9 becomes IX, keeping numbers short instead of writing IIII. Only six subtractive pairs are valid, IV, IX, XL, XC, CD, and CM, and no symbol repeats more than three times, so the system stays unambiguous. This converter applies those rules in both directions and checks its own answer, so you'll always get a standard, valid result. You don't have to remember the pairs, since it's all worked out for you, and you won't accidentally write IIII, because it's flagged as non-standard. That's the part that trips people up when they're writing a date by hand.
Converting, step by step
Here's the quick routine, either direction:
- 1
Type your valueEnter a number, or type Roman numerals; it'll detect which.
- 2
Read the resultYou'll see the conversion the other way, up top.
- 3
Check the breakdownSee how the symbols or values add up.
- 4
Copy itTap copy and it's on your clipboard, ready to use.
The Roman numeral chart
The seven symbols and the six subtractive pairs that make up every numeral.
| Numeral | Value | Numeral | Value |
|---|---|---|---|
| I | 1 | IV | 4 |
| V | 5 | IX | 9 |
| X | 10 | XL | 40 |
| L | 50 | XC | 90 |
| C | 100 | CD | 400 |
| D | 500 | CM | 900 |
| M | 1000 | MMXXIV | 2024 |
Frequently asked questions
You type either a number or a set of Roman numerals, and the tool figures out which way you're going and converts it. For a number, it works through the values from largest to smallest, adding the matching symbols, so 2024 becomes MMXXIV. For numerals, it reads the symbols left to right, subtracting when a smaller one sits before a larger one, like the IV in IV meaning four. It checks the result both ways, so an invalid string gets flagged rather than guessed.
There are seven: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. Bigger numbers stack these up, and a smaller symbol placed before a larger one means subtract, which is how 9 is written IX and 40 is XL. The chart below lists the key values and the subtractive pairs, so you can read or write any numeral once you know the seven letters.
Standard Roman numerals use subtraction to keep things short, so instead of four ones, 4 is one before five, written IV. The same idea gives 9 as IX, 40 as XL, 90 as XC, 400 as CD, and 900 as CM. Only those six subtractive pairs are allowed, and a symbol does not repeat more than three times in a row, which is why this converter rejects a string like IIII as not standard.
With the standard letters, this converter goes up to 3999, written MMMCMXCIX. That's because M is the biggest single symbol at 1000, and you don't repeat it more than three times, so MMM is 3000 and the rest fills in below 1000. Larger numbers historically used a bar over a letter to multiply it by a thousand, but that's outside the everyday set, so the tool caps at 3999.
Plenty of places: clock faces, book chapters, movie copyright years, the Super Bowl, royal and papal names, and outlines. Reading a year like MCMXCIV on a film is the most common reason people reach for a converter. Once you know the seven symbols and the subtraction rule, the everyday ones come quickly, and the chart here is a handy reminder for the rest.
Yes, it's completely free, with no sign-up, and it runs right in your browser, so nothing you type leaves your device. Convert a number to numerals or numerals to a number, see the breakdown, and check the chart, all in a tap. Bookmark it for homework, tattoos, dates, chapter numbers, or decoding a movie year, and you'll have an accurate conversion whenever you need one.
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