Free Roman Numeral Converter
Convert between numbers and Roman numerals (1–3999) — type in either box.
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).
Is my data sent anywhere?
No. The conversion happens entirely in your browser. Nothing is transmitted or stored.