Roman Numeral Converter
Convert between Roman numerals (I, V, X, L, C, D, M) and decimal numbers. Enter a decimal number (1–3999) to get its Roman form, or type a Roman numeral to see its decimal value — with the value of each symbol broken out.
Enter a number or Roman numeral
Enter a value and press Convert.
Roman numeral symbols
| Symbol | Value |
|---|---|
I | 1 |
V | 5 |
X | 10 |
L | 50 |
C | 100 |
D | 500 |
M | 1000 |
Reading rules
- Symbols are usually written from largest to smallest and their values are added:
XV= 10 + 5 = 15. - When a smaller symbol appears before a larger one, it is subtracted:
IV= 5 − 1 = 4,IX= 10 − 1 = 9,XL= 50 − 10 = 40,XC= 100 − 10 = 90,CD= 500 − 100 = 400,CM= 1000 − 100 = 900. - The subtractive pairs are limited to these six combinations.
- No symbol may be repeated more than three times in a row.
- Standard Roman numerals cover values from 1 to 3999.
Common conversions
| Decimal | Roman |
|---|---|
| 1 | I |
| 4 | IV |
| 9 | IX |
| 40 | XL |
| 90 | XC |
| 400 | CD |
| 900 | CM |
| 2024 | MMXXIV |
| 3999 | MMMCMXCIX |
Worked examples
Example 1 — Decimal to Roman
Convert 1987 to Roman.
1000 = M, 900 = CM, 80 = LXXX, 7 = VII → MCM LXXX VII.
1987 = MCMLXXXVII
Example 2 — Roman to decimal
Convert XLII to decimal.
XL = 40, II = 2 → 42.
XLII = 42
Example 3 — Subtractive notation
Convert MCMXCIX to decimal.
M = 1000, CM = 900, XC = 90, IX = 9 → 1999.
MCMXCIX = 1999
Related calculators
Frequently asked questions
The subtractive notation (IV for 4) shortens the numeral and became standard in the Middle Ages. Some clock faces still use IIII for 4 for visual symmetry with VIII opposite it.
Standard Roman numerals have no symbol for zero and do not represent negative numbers. The system is designed for counting positive values only.
The standard system is limited to 3999 (MMMCMXCIX). Larger values historically used a bar over a symbol to indicate multiplication by 1000, or brackets. Those extended forms are outside the scope of this converter.