Roman Numeral Converter
Convert any number between Roman numerals and standard Arabic numerals (I, II, III ↔ 1, 2, 3).
Decimal → Roman
Roman → Decimal
How to use the Roman Numeral Converter
- Enter your inputs into the Roman Numeral Converter above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The Roman numeral system
I=1, V=5, X=10, L=50, C=100, D=500, M=1000 · · · Smaller before larger subtracts (IV = 4); after, adds (VI = 6)
Standard rules: no more than 3 identical letters in a row (so 4 = IV, not IIII); only I, X, C subtract (no VL or LD). Some variations exist for years on monuments.
Worked example
2026 = MMXXVI (1000 + 1000 + 10 + 10 + 5 + 1). 49 = XLIX (50−10 + 10−1). 1999 = MCMXCIX (1000 + 1000−100 + 100−10 + 10−1).
Frequently asked questions
Is there a Roman numeral for zero?
No — Romans didn't have a numeral for zero. Medieval Latin used "nulla" (nothing) in arithmetic tables. The number system simply didn't require it.
What is the largest Roman numeral?
In strict standard, MMMCMXCIX = 3,999. Larger numbers used overlines (V̄ = 5,000) but this is non-standard and rarely encountered.
Where are Roman numerals still used?
Clock faces, book chapters, monument dates, Super Bowl numbers, movie sequels (Star Wars Episode VIII), and pope/king regnal names (Pope John XXIII).