Roman Numeral Converter

How Roman numerals work

Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1,000. You write a number from the largest value to the smallest and add them up: MDCLXVI = 1,000 + 500 + 100 + 50 + 10 + 5 + 1 = 1,666.

To avoid four of the same letter in a row, a smaller numeral placed before a larger one is subtracted. Only six pairs are used: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900. So 1994 is M + CM + XC + IV = MCMXCIV, and 2026 is MM + XX + VI = MMXXVI.

The easy way to convert a number is to go place by place. 3,888 is 3,000 (MMM) + 800 (DCCC) + 80 (LXXX) + 8 (VIII) = MMMDCCCLXXXVIII, the longest numeral below 4,000.

Rules for valid Roman numerals

I, X, C and M can repeat up to three times in a row; V, L and D never repeat. Only I, X and C are used to subtract, and only from the next two larger letters: I from V and X, X from L and C, C from D and M. That is why 99 is XCIX, not IC, and 49 is XLIX, not IL.

The converter checks these rules. Type IIII and it tells you the standard form is IV; type VV and it suggests X. Clock faces often show IIII for four, and older inscriptions break the rules too, but the subtractive form is the standard used in books, film credits and legal documents today.

There is no Roman numeral for zero, negative numbers or fractions in this system. Medieval writers used the word nulla, or N, for zero.

Large numbers: the bar (vinculum)

Standard Roman numerals stop at 3,999 (MMMCMXCIX) because 4,000 would need four M’s. For bigger numbers the Romans drew a bar, called a vinculum, over a numeral to multiply it by 1,000: V̅ = 5,000, X̅ = 10,000, C̅ = 100,000 and M̅ = 1,000,000.

This converter uses the bar from 4,000 up: 4,000 is I̅V̅, 25,000 is X̅X̅V̅ and 3,999,999 is M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX. The bar is a combining overline character, so it copies into most apps, but some fonts draw it slightly off center.

Years, dates and common uses

Roman numerals still show up on clock faces, building cornerstones, book chapters, monarchs and popes (Charles III, Leo XIV), movie copyright years and the Super Bowl, which became Super Bowl LX in 2026. The current year, 2026, is MMXXVI; 2000 is MM, 1999 is MCMXCIX and 1776 is MDCCLXXVI.

For a date, convert the month, day and year separately. In the US order, July 4, 1776 is VII.IV.MDCCLXXVI, and October 29, 2026 is X.XXIX.MMXXVI. Check the order before you engrave or tattoo a date: most of the world writes the day first (XXIX.X.MMXXVI).