Roman numeral converter
Type a number to get its Roman numeral, or type a Roman numeral to read it as a number. The converter shows how the numeral is built and tells you when a numeral is not written the standard way.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Type a number from 1 to 3999, for example 2026, to get MMXXVI.
- Or type a Roman numeral, for example XLII, to get 42. Upper and lower case both work.
- The breakdown shows each decimal place on its own, and the result can be copied.
The rules
| Symbol |
I |
V |
X |
L |
C |
D |
M |
| Value |
1 |
5 |
10 |
50 |
100 |
500 |
1000 |
- Each decimal place is written on its own, from thousands down to ones.
- I, X, C and M can repeat up to three times; V, L and D never repeat.
- Only six subtractive pairs exist: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
The converter accepts only numerals written by these rules. Forms such as IIII, VX, IC or XM are reported as non-standard, with the standard spelling of the value when there is one (IC would be 99, written XCIX).
Worked example
1994: 1000 = M, 900 = CM, 90 = XC, 4 = IV, so 1994 = MCMXCIV. Reading it back: M (1000) + CM (900) + XC (90) + IV (4) = 1994.
Where you meet them
- Years on buildings and in film credits (MMXXVI is 2026).
- Clock faces, book chapters, monarchs and popes (Louis XIV), and events such as the Super Bowl.
- Outlines and lists: i, ii, iii in lowercase.
Frequently asked questions
How do Roman numerals work?
Seven letters stand for 1, 5, 10, 50, 100, 500 and 1000 (I, V, X, L, C, D, M). Letters are added from left to right, largest first, but a smaller letter before a larger one is subtracted. 4 is IV and 9 is IX. Each decimal place is written separately, so 1994 is M + CM + XC + IV = MCMXCIV.
Why only up to 3999?
Without extra symbols the largest number is MMMCMXCIX = 3999, because a letter may repeat only three times in a row. Larger numbers were written with a bar over a letter (×1000), which is not part of the standard form.
Why is IIII rejected? I have seen it on clocks.
Clock faces often use IIII for 4 for visual balance, but the standard notation is IV. The converter tells you the standard form instead of guessing.
Is there a zero in Roman numerals?
No. The Roman system has no symbol for zero and no negative numbers or fractions in this form.
Can I type lowercase letters?
Yes, mcmxciv is read the same as MCMXCIV.