How to use it
- Type a whole number from 1 to 3,999 in the left box; the Roman numeral appears on the right.
- Or type a Roman numeral on the right — upper or lower case — and its value appears on the left.
- The line below breaks the value into parts, for example 1994 = 1000 (M) + 900 (CM) + 90 (XC) + 4 (IV).
- If a numeral is valid but not written the standard way, the tool tells you its value and the standard spelling.
The rules of Roman numerals
Seven letters carry the values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. A number is written from the largest value down, and the values are added: 2026 is MM + XX + VI = MMXXVI.
Subtraction
To avoid four identical letters in a row, a smaller symbol placed before a larger one is subtracted. Only six such pairs are used in the standard form: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). So 4 is IV rather than IIII, and 1994 is MCMXCIV. Each power of ten can only be subtracted from the next two symbols: I from V and X, X from L and C, C from D and M.
Why stop at 3,999?
With these rules the largest number is MMMCMXCIX, 3,999; 4,000 would need MMMM. Larger numbers were written in Roman times with a bar over a numeral to multiply it by a thousand (the vinculum), and in other ways, but there was never one agreed system, so this converter keeps to the standard range. There is also no symbol for zero.
Strict reading
A loose reader would accept IIII, VV or IC by simply adding and subtracting. Clock faces often show IIII, and old inscriptions are not always consistent. When checking a date on a document or a film copyright line, though, it helps to know whether a numeral is correctly formed. The converter computes the value by the usual rule, converts it back to the standard form and reports a mismatch: IIII is 4 written as IV, and IC is 99 written as XCIX.
Examples
| Number | Roman numeral | Breakdown |
|---|---|---|
| 4 | IV | 5 − 1 |
| 9 | IX | 10 − 1 |
| 40 | XL | 50 − 10 |
| 1994 | MCMXCIV | 1000 + 900 + 90 + 4 |
| 2026 | MMXXVI | 1000 + 1000 + 10 + 10 + 5 + 1 |
| 3999 | MMMCMXCIX | 3000 + 900 + 90 + 9 |
Every number from 1 to 3,999 has been checked to convert to a Roman numeral and back to the same number.
Limits
- Range 1–3,999. Zero, negative numbers, fractions and numbers above 3,999 have no standard Roman form.
- Standard forms only. Historical variants such as IIII on clocks or VIIII for 9 are reported as non-standard, together with their value and the standard spelling.
- Unicode Roman numeral characters (such as Ⅻ, a single character) are not read; type them as ordinary letters.
Frequently asked questions
What is 2026 in Roman numerals?
MMXXVI: two thousands (MM), two tens (XX), a five and a one (VI).
Why do some clocks show IIII instead of IV?
It is a long-standing clockmaking convention, often explained as visual balance with VIII opposite. It is not the standard form, and the converter flags it as such.
Is there a Roman numeral for zero?
No. The Roman system had no symbol for zero.
How are numbers above 3,999 written?
Historically with a bar over a numeral to multiply it by 1,000, among other conventions. There is no single standard, so this tool stops at 3,999.
Does case matter?
No. mcmxciv and MCMXCIV are both read as 1994.