Roman Numeral Converter
Convert between regular numbers and Roman numerals in both directions.
Comment ça marche
Roman numerals use seven letters to represent values: I=1, V=5, X=10, L=50, C=100, D=500, and M=1000. Combining them in a specific way lets any number from 1 to 3999 be written using just these seven symbols.
Converting a number to Roman numerals works by repeatedly subtracting the largest possible symbol value (including special two-letter combinations like CM=900 and IX=9) and appending that symbol, until nothing remains. For 2026: subtract 1000 (M), subtract 1000 again (M), subtract 10 (X), subtract 10 again (X), subtract 5 (V), subtract 1 (I) — giving MMXXVI.
The subtractive notation (like IV for 4, or IX for 9) is what makes reading Roman numerals occasionally tricky: a smaller symbol placed before a larger one means subtract, while a smaller symbol placed after means add. IV is 4 (5 minus 1), while VI is 6 (5 plus 1) — the position of the smaller symbol relative to the larger one completely changes the value.
Converting the other direction — Roman numerals back to a number — works by scanning left to right and adding each symbol's value, except when a smaller value appears immediately before a larger one, in which case it's subtracted instead. This correctly handles both the additive (VI, XII) and subtractive (IV, IX, XL) patterns.
Standard Roman numerals cap out at 3999 (MMMCMXCIX), because there's no standard single symbol for 5,000 in common modern usage, and stacking more than three or four M's becomes impractical — some historical systems used a bar over a numeral (vinculum) to multiply its value by 1,000 for larger numbers, but this isn't standard in everyday use.
Roman numerals persist today in specific contexts: clock and watch faces, book chapter or preface numbering, monarch and pope names (Elizabeth II, Louis XIV), Super Bowl numbering, and copyright years in film credits — mostly stylistic or traditional choices rather than practical necessity in the modern number system.
What's the largest number supported?
Standard Roman numerals go up to 3999 (MMMCMXCIX).
Why does IV mean 4 instead of 6?
Because a smaller numeral placed before a larger one is subtracted (I before V means 5−1=4), while a smaller numeral placed after is added (VI means 5+1=6) — position relative to the larger symbol determines the meaning.
Is there a Roman numeral for zero?
No — the classical Roman numeral system has no symbol for zero, which wasn't part of Roman mathematics; zero as a concept and symbol developed later in other number systems.
Why do Super Bowls and movie credits use Roman numerals?
It's largely a stylistic and traditional convention that adds a sense of formality or timelessness, though the underlying reason is more habit and branding than mathematical necessity.
How do I write large numbers like 5,000 or 10,000 in Roman numerals?
Standard everyday Roman numerals don't go beyond 3999; historically, a bar drawn over a numeral (vinculum) multiplied its value by 1,000 for larger numbers, though this isn't commonly used today.
Why does 2026 convert to MMXXVI?
M+M (2000) + X+X (20) + V+I (6) = 2026 — each symbol subtracted from the running total in descending order of value.
Are there different valid ways to write the same Roman numeral?
No — standard modern usage follows strict rules (like never repeating a symbol more than three times in a row, and using subtractive notation for 4 and 9) that produce exactly one correct representation for each number.
How were Roman numerals actually used by the ancient Romans?
They were used for counting, commerce, and inscriptions throughout the Roman Empire — but Roman mathematicians typically performed actual arithmetic using counting boards or an abacus rather than manipulating the numerals directly, since Roman numerals are cumbersome for calculation.
Can I convert a Roman numeral with lowercase letters?
This converter expects standard uppercase letters (I, V, X, L, C, D, M) — convert lowercase input to uppercase first if needed.