Roman numeral converter

How to convert between numbers and Roman numerals

Split the number into thousands, hundreds, tens and ones, and write each part in Roman letters: 2026 = 2000 + 20 + 6 = MM + XX + VI = MMXXVI. To read a numeral, add the letter values, subtracting any letter that stands before a larger one: MCMXCIV = 1000 + 900 + 90 + 4 = 1994.

Roman numeral letters and subtractive pairs

Seven letters supply every value. The system has no zero and no place-value digits, so a numeral is a sum of letter values.

Standard form writes values from largest to smallest and adds them: XVI = 10 + 5 + 1 = 16. Six pairs subtract instead: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900.

I, X, C and M repeat at most three times in a row, and V, L and D never repeat. That is why 4 is IV, not IIII, and why the largest standard numeral is 3999, MMMCMXCIX.

How to write a number in Roman numerals

Convert one place value at a time and join the parts. 1994 = 1000 + 900 + 90 + 4 = M + CM + XC + IV = MCMXCIV, and 49 = 40 + 9 = XL + IX = XLIX.

A letter is subtracted only from the next two larger letters: I from V and X, X from L and C, C from D and M. So 49 is not IL, and 99 is XCIX, not IC.

Roman numbers chart: 1 to 100 and common years

Every number from 1 to 100, then subtractive examples, well-known years and 3999, the largest standard numeral:

Overlines for numbers above 3,999

An overline, or vinculum, multiplies the letters under it by 1000: 4000 is I̅V̅, 5000 is V̅ and 50,000 is L̅. In 4026 = I̅V̅XXVI, only the thousands are overlined.

The notation reaches 3,999,999, written M̅M̅M̅C̅M̅X̅C̅I̅X̅CMXCIX. MMMM breaks the three-repeat rule: it reads as 4000, but the standard form is I̅V̅.

In typed text, each overlined letter is followed by a combining overline character, U+0305 in Unicode. A bar typed before a letter, or underscore notation such as _V, is not an overline.

Nonstandard numerals such as IIII and IC

Numerals are read with one rule: subtract a letter that is smaller than the letter after it, and add every other letter. That gives IIII = 4, IC = 99 and IIV = 5, whose standard spellings are IV, XCIX and V.

A value is not a validity check. Clock faces often show IIII for four, but IC is not standard form. For schoolwork, chapter headings or an inscription, use the standard spelling.

Writing years and dates in Roman numerals

A year is one number: 2026 is MMXXVI and 1776 is MDCCLXXVI. For a full date, convert the day, month and year separately. In day/month/year order, 3 October 2026 becomes III, X and MMXXVI, joined with whatever separator you use, such as III.X.MMXXVI.

To count the days between two dates, use the days between dates calculator.

Checking with Excel

Excel's ROMAN function returns the classic form by default: =ROMAN(499) gives CDXCIX. Its optional form argument produces shorter, nonstandard spellings, so check which form a spreadsheet used.

The ARABIC function converts back: =ARABIC("LVII") gives 57 and =ARABIC("mcmxii") gives 1912. ARABIC returns 0 for an empty string, although Roman numerals have no zero.

What you can type

• Upper or lower case, with or without spaces: mcmxciv and MC MXCIV both read as 1994.
• Only the letters I, V, X, L, C, D and M. Unicode numeral characters such as Ⅳ, and text such as "Chapter IV", are not read.
• Whole numbers from 1 to 3,999, or up to 3,999,999 with the overline option. Zero, negative numbers and fractions have no Roman form.