Type a number to get its Roman numeral, or type a Roman numeral to get the number. It works for 1 to 3,999, the range of standard Roman numerals.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Roman numeral converter works
Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000.
Number to Roman: the calculator works from the largest value down. It uses the subtractive pairs IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900), and writes each place value in turn. For example, 1,994 is M + CM + XC + IV.
Roman to number: it reads left to right, adding each letter, but subtracting a letter when a larger one follows it. It then converts the answer back to Roman and compares. If they differ, the input is not in standard form and you are told so, with the correct form if the meaning is clear. So IIII and IC are rejected, while IV and XCIX are accepted.
Range: 1 to 3,999 only. There is no Roman zero, and the largest standard numeral is MMMCMXCIX. Larger numbers need an overline convention, which is not supported here. Letters can be upper or lower case.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Number or Roman numeral | 2026 |
Roman numeral for 2,026: MMXXVI
| Built from | M + M + X + X + V + I |
|---|---|
| Number | 2,026 |
Tips and common mistakes
Roman numerals are common on clocks, film and TV copyright dates, book chapters and monarchs’ names. Type a year to get its numeral quickly, for example when checking a date on a building.
A letter is never repeated more than three times in a row, and only I, X and C are used as the smaller part of a subtractive pair. If the tool says your numeral is invalid, check for patterns such as VX or IIII, and look at the corrected form it suggests.
Frequently asked questions
Why does the converter stop at 3,999?
Standard Roman numerals have no letter above M, and a letter is not repeated more than three times, so the largest number is MMMCMXCIX.
Is there a Roman numeral for zero?
No. The Roman system had no symbol for zero, so the converter asks for a number of 1 or more.
Why is IIII or IC rejected?
They are not standard form. Four is written IV, and 99 is XCIX, because only I, X and C can be subtracted and only from the next two larger letters.