Quick Answer
Roman numerals are built from seven symbols, I=1, V=5, X=10, L=50, C=100, D=500, M=1000, added together left to right, except when a smaller symbol appears before a larger one, in which case it's subtracted (as in IV=4 or IX=9).
What Is Roman Numerals?
Roman numerals are the numbering system used in ancient Rome and still seen today on clock faces, book chapters, movie sequel titles, monarch names (Queen Elizabeth II), and Super Bowl numbering. Unlike the Arabic numeral system (0-9) used for everyday counting, Roman numerals have no zero and no place values, instead, each symbol has a fixed value, and numbers are built by combining symbols according to specific addition and subtraction rules.
The system uses seven base symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Reading left to right, symbols are normally added together (VI = 5+1 = 6). But when a smaller-value symbol appears immediately before a larger one, it's subtracted instead of added (IV = 5−1 = 4), this subtractive rule is what keeps numbers like 4, 9, 40, 90, 400, and 900 from requiring four or more repeated symbols in a row.
This calculator converts in both directions: enter any number from 1 to 3999 (the practical range for standard Roman numerals) to see its Roman form, or enter a Roman numeral to see its Arabic (regular number) equivalent.
How to Use
- 1Choose a conversion direction, Number to Roman, or Roman to Number.
- 2For Number to Roman: enter any whole number from 1 to 3999.
- 3For Roman to Number: type the Roman numeral using capital letters (I, V, X, L, C, D, M).
- 4The result updates instantly as you type.
Formula
I=1 V=5 X=10 L=50 C=100 D=500 M=1000IV=4 IX=9 XL=40 XC=90 CD=400 CM=900A smaller numeral before a larger one is subtracted; a smaller numeral after a larger one is addedExample: Converting the year 2024 to Roman numerals
- 2000 = MM (M + M, since 1000+1000)
- 24 = XX (10+10) + IV (5−1)
- Combine: MM + XX + IV
Tips & Things to Know
- Standard Roman numerals only go up to 3,999 (MMMCMXCIX), numbers at or above 4,000 traditionally require a special notation (a bar over a numeral to multiply it by 1,000), which isn't part of everyday usage.
- A symbol is never repeated more than three times in a row (III is fine, but 4 is IV, never IIII, in classical/standard usage), this is what the subtractive rule exists to prevent.
- Only specific smaller-before-larger pairs are valid for subtraction: I before V or X, X before L or C, and C before D or M. Combinations outside this pattern (like IL for 49) are not standard notation, 49 is correctly XLIX.
- Roman numerals are still commonly used today for chapter/section numbering, clock faces, the naming of monarchs and popes (Elizabeth II, Louis XIV), and sequels or annual events (Super Bowl LVIII).