Roman numeral converter

What are Roman numerals?

Roman numerals are the number system used in ancient Rome, built from combinations of seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Despite being thousands of years old, they're still used today on clock faces, in movie and TV copyright years, for book chapter and outline numbering, and to number monarchs, popes, and Super Bowls.

How to use this converter

1. Use the first box to convert an ordinary (Arabic) number into Roman numerals.
2. Use the second box to convert a Roman numeral back into a regular number.

Both fields update live as you type, so you can experiment freely and see results instantly.

How Roman numerals are built

Roman numerals are formed by combining symbols and adding their values together, generally written from largest to smallest, left to right. For example, XVI = X (10) + V (5) + I (1) = 16.

The subtractive rule

Roman numerals mostly work by simple addition (VI = 5+1 = 6), but for six specific cases a smaller symbol placed before a larger one means subtraction instead: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). This is why 4 is written "IV" (5 − 1) rather than "IIII", and why 40 is "XL" (50 − 10) rather than "XXXX".

Worked examples

Converting a number to Roman numerals

1994 breaks down as 1000 (M) + 900 (CM) + 90 (XC) + 4 (IV) = MCMXCIV.

Converting Roman numerals to a number

MMXXIV breaks down as M (1000) + M (1000) + X (10) + X (10) + IV (4) = 2024.

Symbol reference chart

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

Common uses

• Reading copyright years at the end of movies and TV shows
• Numbering book chapters, outline sections, or appendices
• Understanding names like "Super Bowl LVIII" or "Elizabeth II"
• School assignments covering ancient number systems
• Reading clock faces and monument inscriptions that use Roman numerals

Limits of this converter

• Standard Roman numerals only go up to 3,999 (MMMCMXCIX) — there's no standard symbol for larger numbers without special notation (like a bar over a letter to multiply it by 1,000)
• There is no Roman numeral for zero — the concept of zero as a number wasn't part of the classical Roman system
• Only whole numbers are supported — Roman numerals don't have a standard way to represent fractions or decimals

Frequently asked questions

What happens if I enter an invalid Roman numeral?

The converter will flag it, since not every combination of letters follows valid Roman numeral construction rules (for example, "IIII" or "VV" aren't standard forms).

Why do some clocks show "IIII" instead of "IV" for four?

This is a traditional clockmaking convention, not a numeral system rule — some clockmakers use "IIII" for visual symmetry with "VIII" on the opposite side of the dial, even though "IV" is the technically correct subtractive form.