Roman Numeral Converter
Convert numbers to Roman numerals and back — 1 to 3999.
The Roman Numeral Converter works in both directions: turn 2025 into MMXXV, or decode MCMLXXXIV back into 1984. It follows the standard modern convention with subtractive pairs (IV for 4, IX for 9, CM for 900) and validates that inputs are in canonical form.
Roman numerals still appear everywhere — movie copyrights, clock faces, outlines, Super Bowl names, monarch titles — and converting them is a classic interview and puzzle exercise. The tool handles the full range 1–3999, where the system works without overlines.
Validation is strict: non-canonical strings like 'IIII' or 'VX' are rejected rather than guessed at, so you always know the numeral is genuinely well-formed. Everything runs locally in your browser.
Roman numeral
MMXXV
How to use the Roman Numeral Converter
- Choose Number → Roman or Roman → Number.
- Enter the number (1–3999) or the numeral.
- Read the converted result instantly.
- Copy it if needed.
- Try years like 1984 (MCMLXXXIV) or 2025 (MMXXV).
Frequently asked questions
How do Roman numerals work?
Symbols add up (M=1000, D=500, C=100, L=50, X=10, V=5, I=1), with one subtraction rule: a smaller symbol before a larger one subtracts, so IV=4, IX=9, XC=90 and CM=900.
Why is there no zero in Roman numerals?
The Roman system is additive, not positional — it has no placeholder concept, so zero never existed in it. The modern range therefore starts at 1 (I).
What is the largest number Romans could write?
In classical practice, 3,999 (MMMCMXCIX) was the practical ceiling. Later systems added overlines (a bar multiplies by 1,000) to reach millions — beyond the scope of this converter's standard 1–3999 range.
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