Roman Numeral Converter – Numbers to Roman & Back
Convert numbers to Roman numerals and Roman numerals back to numbers, instantly. Enter a value, and the converter shows the result and checks that any Roman numeral you type is actually valid. Free, no sign-up, and everything runs in your browser.
Enter a whole number from 1 to 3999.
This free Roman numeral converter turns ordinary numbers into Roman numerals and converts Roman numerals back into numbers — both directions, instantly. Type a number to see its Roman form, or type a numeral like MCMXCIV to read its value. Unlike many converters, it also checks that a numeral you enter is genuinely valid, so "IIII" or "VV" are flagged rather than silently accepted. It is made for students learning numerals, teachers preparing lessons, writers dating copyright lines and book chapters, and anyone decoding clock faces, movie credits, or monuments. Everything runs in your browser, with no sign-up, and your last entry is saved locally. Enter a value above to convert it.
What does this tool do?
It converts between numbers and Roman numerals in both directions, over the standard range of 1 to 3,999:
- Number to Roman — for example, 2024 becomes MMXXIV.
- Roman to Number — for example, MCMXCIV becomes 1994.
- Validation — if you type a malformed numeral, the tool tells you it is not valid instead of guessing.
Why use this tool?
Roman numerals follow strict rules that are easy to break: a symbol repeats at most three times, and only certain subtractive pairs are allowed. Written by hand, it is easy to produce something like "IIII" or "IC" that looks plausible but is wrong. This converter applies the rules correctly every time, and its validation means you can trust that a numeral is properly formed — useful when accuracy matters, such as in teaching, publishing, or design.
How the tool works
- Number to Roman: the value is reduced using standard symbol values (M, CM, D, CD, C, XC, and so on), appending each symbol until the number reaches zero. This naturally produces the correct subtractive forms like IV, IX, XL, and CM.
- Roman to Number: each symbol is read and added, subtracting when a smaller symbol precedes a larger one (as in IV or CM).
- Validation: after reading a numeral, the tool converts the result back to Roman and compares it to what you typed. If they do not match exactly, the numeral is not valid — this catches errors like IIII, VV, IC, and MMMM.
How to use the tool
- Choose a direction: Number → Roman or Roman → Number.
- Type your value — a number from 1 to 3999, or a Roman numeral.
- Read the converted result instantly below.
- If a Roman numeral is invalid, you will see a clear message.
- Click Copy to reuse the result.
Practical examples
A year
2024 converts to MMXXIV — handy for copyright dates, cornerstones, and title pages.
Decoding a film credit
MCMXCIV in a movie's end credits converts back to 1994.
A chapter or clock
Chapter XIV is 14; the IV on a clock face is 4 — quick to confirm either way.
Catching an error
Type IIII and the tool flags it as invalid — the correct numeral for 4 is IV.
Common use cases
- Students & teachers: learning and checking Roman numerals.
- Writers & publishers: chapter numbers, prefaces, and copyright years.
- Designers: clock faces, monograms, and tattoo or engraving text.
- Everyday decoding: movie credits, building dates, and Super Bowl-style numbering.
Tips & best practices
- Roman numerals cover 1 to 3,999; there is no zero and no standard single-symbol form above that range.
- A symbol repeats at most three times — 4 is IV, not IIII, and 40 is XL, not XXXX.
- Only I, X, and C are used subtractively (IV, IX, XL, XC, CD, CM); V, L, and D are not.
- Use the validation to double-check numerals copied from clocks, credits, or old documents.
Frequently Asked Questions
What range of numbers does it support?
The standard range of 1 to 3,999. Roman numerals have no symbol for zero and no standard basic form for larger values.
Why is IIII invalid when clocks use it?
In standard notation, 4 is written IV. "IIII" appears on some clock faces as a traditional design choice, but it is not the standard numeral, so the tool flags it.
How does the validation work?
The tool converts your numeral to a number, then converts that number back to Roman. If the result does not match exactly what you typed, the numeral is not valid.
Which letters are used?
Seven: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Everything is built from these.
Can it convert years like 1994?
Yes. 1994 is MCMXCIV. Any year from 1 to 3999 converts in either direction.
Is it case sensitive?
No. You can type Roman numerals in lowercase or uppercase; the tool reads them the same way.
Is my data private?
Yes. Conversion happens entirely in your browser. Nothing you type is uploaded to or stored on a server.
Is the tool free?
Completely free, with no account and no limit on how many conversions you make.