Roman Numeral Converter

Convert Roman numerals both ways

The Roman Numeral Converter turns ordinary numbers into Roman numerals and decodes Roman numerals back into numbers. Type in either box and get the instant result, validated so you know the numeral is correctly formed. It covers the standard range of 1 to 3999.

How Roman numerals work

Roman numerals use seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Values are generally added together from largest to smallest — so MMXXIV is 1000 + 1000 + 10 + 10 + (5 − 1) = 2024. The subtractive rule (like IV for 4 and IX for 9) keeps numerals compact by placing a smaller value before a larger one.

The seven symbols

Symbol	Value
I	1
V	5
X	10
L / C	50 / 100
D / M	500 / 1000

How to use it

1. Enter a number (1–3999) to get its Roman numeral.
2. Or type a Roman numeral to get the number.
3. Copy the converted result.

The subtractive rule

Rather than writing IIII for 4, Romans used IV — a smaller symbol before a larger one means subtract. The valid subtractive pairs are IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). This converter only accepts properly formed numerals, so it rejects invalid combinations and confirms when a numeral is correct.

Where Roman numerals appear

• Clock faces and watch dials.
• Book chapters, outlines, and prefaces.
• Movie sequels and copyright years.
• Super Bowl numbers and monument inscriptions.

Why the 3999 limit?

Standard Roman numerals only go up to 3999 (MMMCMXCIX) because there's no single symbol for 5000 or higher — writing larger numbers requires special overline notation that isn't part of everyday use. For any number in the common range, this converter handles it instantly and accurately.

Private and free

All conversion runs in your browser — nothing is uploaded. The tool is completely free with no sign-up.