Convert numbers to Roman numerals or Roman numerals back to numbers.
Roman numerals are a number system from ancient Rome using letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. This tool converts between Roman numerals and standard numbers.
Despite being replaced by Arabic numerals for practical math roughly a thousand years ago, Roman numerals persist in specific modern contexts: naming monarchs and popes (Elizabeth II, John Paul II), numbering Super Bowls and Olympic Games, marking chapter or volume numbers in books, copyright dates in film credits, and clock faces, where the aesthetic tradition has simply stuck around. Converting between the two systems by hand requires memorizing the value of each symbol (I=1, V=5, X=10, L=50, C=100, D=500, M=1000) and the subtractive notation rule, where a smaller numeral placed before a larger one subtracts rather than adds (IV = 4, not 6).
The subtractive rule is the part that trips people up most - IX means 9 (10 minus 1), but XI means 11 (10 plus 1), and the position of the smaller numeral relative to the larger one is what determines whether it's added or subtracted.
The Roman numeral system predates the concept of zero as a number reaching Europe (zero arrived in Western mathematics later, largely through Arabic and Indian mathematical traditions), which is why there's no symbol for it in classical Roman numerals - a limitation that made certain calculations genuinely difficult for Roman mathematicians and is part of why the system was eventually replaced for practical arithmetic.
Roman numerals use combinations of seven letters — I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) — combined using both an additive and subtractive principle to represent numbers. Generally, letters are added together when arranged from largest to smallest (VI = 5+1 = 6), but a smaller value placed immediately before a larger one is subtracted instead (IV = 5-1 = 4), which is the source of most confusion when learning to read or write Roman numerals correctly.
The subtractive principle only applies to specific letter pairs by convention — I can precede V or X, X can precede L or C, and C can precede D or M — meaning not every smaller-before-larger combination is actually valid Roman numeral notation, which is why writing something like "IL" for 49 (rather than the correct XLIX) is considered incorrect despite superficially following the subtractive pattern.
Despite being replaced by Arabic numerals for practical mathematics centuries ago, Roman numerals persist in specific contexts valued for their formal or traditional appearance: clock faces, movie copyright years in film credits, monarch and pope naming conventions (like Elizabeth II or Pope Francis), book chapter numbering, and the numbering of major sporting events like the Super Bowl, where the Roman numeral has become part of the event's branding identity.
Standard Roman numerals become unwieldy for very large numbers, since the system as commonly used today caps out around 3,999 (MMMCMXCIX) without additional notation. Historically, a bar placed over a numeral multiplied its value by 1,000 to represent larger figures, though this convention is rarely used in modern contexts, which are almost always limited to smaller, everyday numbers like dates or chapter numbers.
Standard Roman numerals support numbers from 1 to 3999.
No, the classical Roman numeral system has no symbol for zero, since it predates the concept reaching Western mathematics.
Standard notation typically goes up to 3,999 (MMMCMXCIX), though extended notations using a bar over a numeral (to multiply by 1,000) exist for larger numbers.
This is the subtractive rule - when a smaller numeral appears before a larger one, it's subtracted rather than added, so IV (1 before 5) equals 4.
