Roman Numeral Converter - Numbers to Roman Numerals

About the Roman Numeral Converter

Roman numerals are still all around us: on clock faces, in the copyright year at the end of films, on the cornerstones of buildings, in the names of monarchs and popes, on chapter headings and outlines, and in the numbering of sporting events. Reading them — or writing a number correctly — means knowing seven letters and the rules for combining them, and a single misplaced letter changes the value.

This Roman numeral converter turns numbers from 1 to 3,999 into Roman numerals, or reads Roman numerals back into numbers. It shows a breakdown of each symbol group, and when reading a numeral it checks that it is written in the standard form, rejecting non-standard forms such as IIII or IC.

How to Use the Roman Numeral Converter

Choose Number to Roman or Roman to number.

For number to Roman, enter a whole number from 1 to 3,999.

For Roman to number, type the numeral using the letters I, V, X, L, C, D and M. Upper or lower case both work.

The result appears with a breakdown of how it is built.

The Symbols

  I = 1      V = 5      X = 10     L = 50
  C = 100    D = 500    M = 1,000

  Subtractive pairs:
  IV = 4     IX = 9     XL = 40    XC = 90
  CD = 400   CM = 900

The Rules

Symbols are written from largest to smallest and their values added: VI is 5 + 1 = 6, and MDC is 1,000 + 500 + 100 = 1,600.

When a smaller symbol comes before a larger one, it is subtracted, but only in six standard pairs: IV, IX, XL, XC, CD and CM. So 4 is IV, not IIII, and 90 is XC.

A symbol can be repeated up to three times in a row: III is 3, CC is 200, CCC is 300. V, L and D are never repeated, because VV would simply be X.

Step-by-Step Example

2024 to Roman numerals.

  2,000 = MM
     20 = XX
      4 = IV
  → MMXXIV

1994 to Roman numerals.

  1,000 = M
    900 = CM
     90 = XC
      4 = IV
  → MCMXCIV

XLII to a number.

  XL = 40,  II = 2  →  42

Common Numbers

  1  I        10  X         100  C          1,000  M
  4  IV       40  XL        400  CD         2,000  MM
  5  V        50  L         500  D          3,000  MMM
  9  IX       90  XC        900  CM         3,999  MMMCMXCIX

Recent years: 1999 is MCMXCIX, 2000 is MM, 2010 is MMX, 2020 is MMXX and 2025 is MMXXV.

Why Standard Form Matters

Historically, Romans were not always consistent; inscriptions show IIII for 4 and even XIIX for 18. Today, a standard form is used everywhere, and forms such as IC for 99 or IIX for 8 are treated as errors — 99 is XCIX and 8 is VIII. The converter reads numerals strictly, so a typo that produces a non-standard numeral is reported rather than silently turned into a number.

The one familiar exception is on clock faces, many of which show IIII instead of IV for four o'clock. This is a long-standing tradition, often said to balance the design against VIII on the opposite side.

Beyond 3,999

Standard Roman numerals stop at 3,999, MMMCMXCIX, because M can only be repeated three times. The Romans wrote larger numbers by drawing a bar, called a vinculum, over a numeral to multiply it by 1,000, so a barred V meant 5,000 and a barred X 10,000. That notation is rarely used today and is not supported here. There was also no symbol for zero; medieval writers sometimes used N, for nulla, meaning nothing.

Where Roman Numerals Are Used Today

Roman numerals appear in the names of monarchs and popes, such as Elizabeth II; in the numbering of events such as the Olympic Games; in film and television copyright years; on watch and clock dials; for book volumes, chapters and prefaces, often in lower case; and in outlines and legal documents. Reading them quickly is mostly a matter of recognising the subtractive pairs.

Reading Long Numerals Quickly

To read a long numeral, split it into thousands, hundreds, tens and units, reading from the left. Each group uses its own letters: M for thousands; C, D and M for hundreds; X, L and C for tens; and I, V and X for units. So MDCCCXLVIII splits into M (1,000), DCCC (800), XL (40) and VIII (8), giving 1,848 — a long numeral for a year, yet one that breaks down quickly once it is grouped. Looking for the subtractive pairs first, such as CM or XC, prevents the most common reading mistake of adding a letter that should be subtracted.

Lower-Case Numerals

Roman numerals are often written in lower case, especially for book prefaces, lists and footnotes: i, ii, iii, iv and so on. The values and rules are identical, and the converter accepts either case.

Understanding Your Result

The headline is the Roman numeral, or the number it represents.

The breakdown line shows each group of symbols with its value.

The check line shows the numeral's length, or the numeral written back in standard form.

The worth knowing line explains the relevant rule.

When Should You Use This Calculator?

Use it to read dates on buildings, films and monuments.

Use it to write a year or number for an invitation, tattoo or engraving.

Use it for monarchs, popes, events and book chapters.

Use it for maths and history homework.

Common Mistakes

Repeating a symbol four times. Write IV, not IIII, and 90 as XC, not an L followed by four X's.

Using non-standard subtraction. 99 is XCIX, not IC.

Repeating V, L or D. VV is written X, and LL is C.

Reading left to right without subtracting. In XC, the X comes off the C.

Expecting numbers above 3,999. Standard notation cannot write them without the bar notation.

Mixing up similar letters. D is 500 and C is 100; a quick check of the breakdown catches most slips.