What Roman numerals are
Roman numerals are a numbering system that started in ancient Rome and is still all around us: on clock faces, in book chapters, on movie copyright dates and in the Super Bowl’s edition number. Instead of ten digits, the system uses seven letters from the Latin alphabet, each with a fixed value: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000.
This converter works both ways. Type a number from 1 to 3999 and you get its Roman form instantly; type a Roman numeral and you get its value in digits. Everything runs in your browser, so nothing is ever uploaded to a server.
How to use the converter
- To go from digits to Roman, type a whole number between 1 and 3999 in the left field.
- To go from Roman to digits, type the letters in the right field (upper or lower case both work).
- Read the answer in the dark result card and hit Copy to grab it.
- If you enter a number out of range or a malformed numeral, a clear error message tells you what to fix.
How Roman numerals are built
Letters are written from the largest value to the smallest and then added together: VIII is 5 + 1 + 1 + 1 = 8. The key twist is subtractive notation: when a smaller letter sits right before a larger one, you subtract it. That is why 4 is IV (5 minus 1) rather than IIII, and 9 is IX (10 minus 1). The same idea gives 40 (XL), 90 (XC), 400 (CD) and 900 (CM).
Two rules keep things tidy: never repeat the same letter more than three times in a row, and only I, X and C may be subtracted (never V, L or D). That is why IIII, VV and IC are invalid.
Worked example
Let’s convert 2024 step by step:
- 2000 is two thousands:
MM - 20 is two tens:
XX - 4 is five minus one:
IV
Put the pieces together and MM + XX + IV = MMXXIV. A trickier case with two subtractions is 1984, which becomes M + CM + LXXX + IV = MCMLXXXIV.
Key symbol table
| Number | Roman |
|---|---|
| 1 | I |
| 4 | IV |
| 5 | V |
| 9 | IX |
| 10 | X |
| 40 | XL |
| 50 | L |
| 90 | XC |
| 100 | C |
| 500 | D |
| 1000 | M |
Frequently asked questions
How do I write the current year in Roman numerals?
The year 2026 is MMXXVI: two thousands (MM), two tens (XX), a five (V) and a one (I). For reference, 2024 is MMXXIV and 2025 is MMXXV.
Why is 4 written IV and not IIII?
Because the standard system uses subtractive notation to avoid repeating a letter four times. You will still spot IIII on some clock faces as a stylistic tradition, but the correct, universal form is IV. This converter only accepts the standard form.
Is there a zero in Roman numerals?
No. The Roman system has no symbol for zero or for negative numbers; it was built for counting quantities, not for positional arithmetic. The concept of zero reached Europe much later, along with the Arabic numerals we use today.
How are numbers larger than 3999 written?
In the basic form, 3999 (MMMCMXCIX) is the ceiling, because four Ms in a row are not allowed. For bigger values the Romans drew a bar (a vinculum) over a letter to multiply it by a thousand. That extended notation is outside the scope of this tool.