Roman Numeral Converter
Convert any number from 1 to 3,999 to and from Roman numerals. Includes a quick reference table and common examples.
| Symbol | Value | Subtractive use |
|---|---|---|
| I | 1 | IV = 4, IX = 9 |
| V | 5 | — |
| X | 10 | XL = 40, XC = 90 |
| L | 50 | — |
| C | 100 | CD = 400, CM = 900 |
| D | 500 | — |
| M | 1,000 | — |
How Roman numerals work
Seven letters, each with a fixed value: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. Numbers are formed by adding or subtracting these in specific combinations.
Additive principle: write symbols from largest to smallest, summing their values. MCXII = 1000 + 100 + 10 + 1 + 1 = 1,112.
Subtractive principle: a smaller numeral placed before a larger one is subtracted. IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. This is what keeps the notation compact — without it, 4 would be IIII (still valid but bulky) and 1999 would need 14 letters instead of 8.
Allowed combinations
Subtractive notation has rules:
- I can subtract before V or X (giving 4 or 9). Not before L, C, D, M.
- X can subtract before L or C (giving 40 or 90). Not before D or M.
- C can subtract before D or M (giving 400 or 900).
- V, L, and D never subtract (they're halfway points and don't need to).
- You can repeat I, X, C, M up to 3 times in a row. Never 4. (So 4 must be IV, not IIII.)
- V, L, and D are never repeated.
A worked example: writing 2026
Walk through largest to smallest:
- 2026 contains 2 thousands → MM (2,000)
- Remaining: 26. No 900s or 500s or 400s.
- 26 contains 2 tens → XX (20)
- Remaining: 6. No 9s.
- 6 = 5 + 1 → VI
- Combine: MMXXVI
A brief history
Roman numerals evolved from earlier Etruscan and Greek tally systems around the 8th century BCE. They were the standard numeral system in Europe for over 2,000 years until Hindu-Arabic numerals (the 0–9 system we use today) gradually replaced them from the 13th–16th centuries.
Why did Hindu-Arabic numerals win? Three reasons: they include zero (essential for place-value math); they're positional (the position of a digit determines its value, like the “hundreds place”); and arithmetic is much easier. Try multiplying MCMLXXIV by XXIV in Roman numerals — you'll quickly see why merchants loved the new system.
Where you still see them
- Movie copyrights — “© MMXXIV”
- Super Bowls — Super Bowl LVIII (58), LIX (59), LX (60).
- Monarchs and popes — Elizabeth II, Pope Francis (numbers used when needed for distinction).
- Watch and clock faces — most fancy analog clocks.
- Building cornerstones — “BUILT MCMXXVII” (1927).
- Book chapter and outline formatting — I, II, III for top-level sections.
- Music theory — chord analysis (I, IV, V chords).
- World Wars — World War I, World War II.
- Olympics — Games of the XXXIII Olympiad (33rd).
- Kentucky Derby — “CL Derby” (150th).
Why the 3,999 ceiling?
With repetition limited to 3, the largest number using only I, V, X, L, C, D, M is 3,999 = MMMCMXCIX. Beyond that, ancient Romans used a horizontal bar above a numeral to multiply by 1,000 (so V̄ would mean 5,000), but this notation isn't reliably rendered in modern fonts and isn't taught in standard usage.
For modern purposes (movie dates, Super Bowls, copyright years), 3,999 is way more than enough — we'd need the year 4000 to break the standard system, which won't happen for a while.