Free Roman Numeral Converter
Convert between numbers and Roman numerals (1–3999) — type in either box.
Reading and writing Roman numerals
Roman numerals combine seven symbols — I (1), V (5), X (10), L (50), C (100), D (500), M (1000) — using two rules at once: repetition adds value (III = 3), and a smaller symbol placed immediately before a larger one subtracts instead of adds (IV = 5 − 1 = 4). Only specific pairs are allowed to subtract this way: I before V or X, X before L or C, and C before D or M. That's why 4 is written "IV" and not the older, non-standard "IIII" — and why this converter's canonical-form check rejects "IIII" as invalid rather than silently accepting it.
Worked example: converting 1994
The greedy algorithm breaks a number into the largest matching chunks, largest first: 1994 = 1000 (M) + 900 (CM) + 90 (XC) + 4 (IV). Concatenated in order, that's MCMXCIV — the number stamped on film reels and buildings to mark the year 1994.
Still in everyday use
- Clock faces — many analog clocks and watches use Roman numerals for the hours.
- Copyright years — movie and TV credits traditionally list the production year in Roman numerals.
- Sequels and events — Super Bowl numbering (Super Bowl LVIII) and sequel titling (Rocky IV).
- Names and titles — monarchs and popes (Elizabeth II, Louis XIV) and generational suffixes.
- Outlines and front matter — book preface pages and formal outline sub-levels.
Frequently Asked Questions
What's the valid range?
1 to 3999. Standard Roman numerals have no symbol for zero and no standalone way to write 4000 or higher without special notation, so this converter sticks to the range the classical system actually supports.
Why does it reject numerals like "IIII" for 4?
Roman numerals have one canonical form per number — 4 is "IV," not "IIII." The converter validates that whatever you type round-trips back to the same numeral, so non-standard or malformed input is rejected rather than silently guessed at.
How does the conversion work?
Numbers are converted by repeatedly subtracting the largest matching Roman value (M, CM, D, CD, C, XC, L, XL, X, IX, V, IV, I) — the standard greedy algorithm. Roman-to-number reads left to right, subtracting a symbol's value when a smaller one precedes a larger one (like IV = 5 − 1).
Do Roman numerals have a symbol for zero?
No. The classical system had no concept of zero as a numeral — it wasn't designed for positional arithmetic the way Arabic numerals are, which is also why there's no standard way to write negative Roman numerals.
Why is 4000 out of range?
The standard subtractive rules top out at M (1000) with no larger base symbol, so numbers past 3999 would require a repeated symbol beyond what the canonical system allows (or non-standard notation like an overline meaning "× 1000"), which this converter doesn't attempt to guess at.
Is my data sent anywhere?
No. The conversion happens entirely in your browser. Nothing is transmitted or stored.