Roman Numeral Converter
Convert numbers to Roman numerals and back. Supports 1 through 3,999,999 using standard and vinculum notation.
What this calculates
Roman numerals show up everywhere — book chapters, movie sequels, copyright years, watch dials, Super Bowls. This converter handles standard form (1-3,999) bidirectionally. Larger numbers use vinculum notation (an overline meaning ×1,000), which we approximate with parentheses.
Formula & how it works
Symbols: 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. Read left to right, sum normally except when a smaller symbol precedes a larger (subtract). Vinculum: bar over a letter multiplies by 1,000 (V̄ = 5,000, etc.). Used for large numbers up to ~4 million.
Worked example
2026 = MM (2000) + XX (20) + VI (6) = MMXXVI. 1994 = M (1000) + CM (900) + XC (90) + IV (4) = MCMXCIV. 49 ≠ IL (illegal — only I before V or X). 49 = XLIX (XL = 40, IX = 9). The subtractive rule has strict limits.
Frequently asked questions
Why no zero?
Romans had no concept of zero as a number. Indian mathematicians introduced it (later transmitted via Arabic). The whole positional decimal system we use today comes from that lineage, while Roman numerals remained additive.
Highest possible Roman numeral?
Standard form maxes out at 3,999 (MMMCMXCIX). Vinculum extends to ~4 million. Beyond that, Roman numerals become impractical — which is why decimal won.
Year MCMLXXXIX?
1989. M = 1000, CM = 900, LXXX = 80, IX = 9. Common movie credit year. Modern films usually use Arabic numerals now, but some artistic productions still go Roman.
Why does the Super Bowl skip 50 in Roman?
Super Bowl 50 (2016) was numbered just '50' rather than 'L' because the NFL felt the single-letter logo was less visually appealing. Returned to Roman with LI in 2017.