Roman Numeral Converter
Convert between Roman numerals and decimal numbers. Supports values from 1 to 3999. Instant two-way conversion.
About Roman Numeral Converter
Convert any decimal number from 1 to 3999 into Roman numerals, or parse Roman numerals back to numbers. Two-way conversion updates instantly as you type. Uses standard subtractive notation (IV for 4, IX for 9, etc.).
Two-Way Conversion
Type a number to get Roman numerals, or type Roman numerals to get the decimal value. Updates in real time.
1 - 3999 Range
Covers all standard Roman numeral values. From I to MMMCMXCIX — everything you need for dates, outlines, and classic references.
Subtractive Notation
Uses the standard IV (4), IX (9), XL (40), XC (90), CD (400), CM (900) patterns. Accurate every time.
Formula Breakdown
See the step-by-step calculation showing how each numeral group adds up — great for learning Roman numeral math.
How It Works
- Enter a number — Type any decimal number between 1 and 3999 in the Number field.
- Or enter Roman numerals — Type Roman numerals using I, V, X, L, C, D, M (case-insensitive).
- Instant conversion — The other field updates immediately. The result panel shows both values.
- View the breakdown — The formula line shows how the number is decomposed into its Roman numeral components.
- Use the reference — Check the quick reference table for numeral values and subtractive notation rules.