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Roman Numerals

Convert numbers to Roman numerals and back for free. Enter 1 to 3999 or a numeral like XIV and get the instant conversion, with validation of proper form.

Convert

Enter an Arabic number (1-3999) or a Roman numeral.

Result

I=1 V=5 X=10 L=50 C=100 D=500 M=1000
Subtractive pairs: IV=4 IX=9 XL=40 XC=90 CD=400 CM=900
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How the conversion works

Roman numerals combine seven letters with an additive and subtractive system: symbols are added left to right, except a smaller symbol before a larger one subtracts, as in IV for 4. The tool applies these rules both ways.

Standard form (1 to 3999) is enforced on encoding, and decoding flags non-standard input like IIII, showing you the correct IIII-free form.

Where Roman numerals still appear

You will meet them on clock faces, book chapter numbers, movie sequel titles, building cornerstones and monarch names. The converter handles all of these everyday cases instantly.

Values above 3999 historically used overlines or parentheses, which this tool does not cover, since standard classroom and publishing use stays within range.

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Roman Numerals FAQs

Why is 4 written as IV and not IIII?
Subtractive notation puts a smaller numeral before a larger one to subtract. IV (5-1) is the standard form; IIII appears on some clocks but is non-standard.
What is the largest number I can convert?
3999 (MMMCMXCIX) in standard form. Larger values need historical extensions like overlines, which are not standard.
Why did my numeral get flagged as non-standard?
Inputs like VIIII or IL are readable but not proper form. The tool shows the value and the correct standard spelling so you learn the rule.
Is zero possible in Roman numerals?
No. The Roman system had no zero symbol, so the tool only accepts 1 and above.
Are lowercase numerals accepted?
Yes. Input is case-insensitive, and the tool outputs traditional uppercase.
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