Roman Numeral Converter

This Roman numeral converter works in both directions. Use it as an arabic to roman numerals tool when you need to write a copyright year, tattoo a date, or label a chapter. Flip the tab and it becomes a roman numeral translator that decodes strings like MCMLXXXIV or LIX back into everyday numbers. The roman numerals calculator accepts any whole value from 1 to 3,999 and any valid letter combination using I, V, X, L, C, D, and M.

Convert an Arabic number to Roman numerals

1. Select the Arabic to Roman tab at the top of the widget.
2. Type the number you want to convert into the input (for example, 2024, 1776, or 49).
3. Read the large Roman numeral in the result card. For 2024 that is MMXXIV.
4. Check the breakdown chips below it to see how each piece maps back: MM = 2000, XX = 20, IV = 4.
5. Scan the quick reference examples for common values like years, ages, and Super Bowl numbers.

Convert Roman numerals to a number

1. Switch to the Roman to Arabic tab.
2. Type the Roman numeral string. The field auto-capitalizes, so you can enter it as mcmxcix or MCMXCIX.
3. The converter validates the sequence. Valid strings show the Arabic number instantly; invalid ones (like IIII, VV, or IC) return an error message.
4. Use this direction when you need roman numerals to number conversion for movie credits, book prefaces, or a historical date.

If you ever wonder what does VII mean or how to write a year in roman numerals, keep the tool open in a browser tab. It handles the edge cases (subtractive pairs, repeated symbols, the 3,999 ceiling) so you do not have to memorize the rules.

Roman numerals are a positional-ish numeral system built from seven letters. Unlike our decimal system, they have no symbol for zero and no concept of place value beyond the order the letters appear. Reading and writing them well comes down to a short set of rules.

The seven symbols and their values

Additive and subtractive rules

Additive: When a larger symbol comes before a smaller one, add them. VI = 5 + 1 = 6. LXVI = 50 + 10 + 5 + 1 = 66. XVII = 10 + 5 + 1 + 1 = 17.

Subtractive: When a smaller symbol comes before a larger one, subtract it. Only six specific pairs are allowed:

• IV = 4 (5 - 1)
• IX = 9 (10 - 1)
• XL = 40 (50 - 10)
• XC = 90 (100 - 10)
• CD = 400 (500 - 100)
• CM = 900 (1000 - 100)

Any other subtractive pairing (like IC for 99 or IL for 49) is invalid in standard notation.

Writing rules: when to repeat, when to subtract

I, X, C, and M can repeat up to three times in a row: III = 3, XXX = 30, CCC = 300, MMM = 3,000. V, L, and D never repeat, because two of them would equal the next letter up (VV would just be X). Subtractive notation exists to avoid four-in-a-row strings: you write IV instead of IIII and IX instead of VIIII.

Algorithm: Arabic to Roman

The converter uses a greedy algorithm. It takes the list of value pairs sorted from largest to smallest (1000 = M, 900 = CM, 500 = D, 400 = CD, 100 = C, 90 = XC, 50 = L, 40 = XL, 10 = X, 9 = IX, 5 = V, 4 = IV, 1 = I), then repeatedly subtracts the largest value that fits and appends its symbol.

Worked example: 1994.

1994 - 1000 = 994    -> M
994  - 900  = 94     -> CM
94   - 90   = 4      -> XC
4    - 4    = 0      -> IV
Result: MCMXCIV

Algorithm: Roman to Arabic

Scan the string left to right. For each letter, look at the next one. If the current letter is smaller than the next, subtract its value; otherwise add it. MCMXCIV becomes: M (1000, next is C, larger, but M > C so add) + CM (C is 100, M is 1000, subtract 100 then add 1000 = 900) + XC (90) + IV (4) = 1994. The tool above also validates by round-tripping the result back to a Roman numeral and comparing.

Upper bound: why 3,999 is the ceiling

Standard Roman numerals stop at 3,999, which is written MMMCMXCIX. To go higher, academic and historical sources use a vinculum, a horizontal bar placed over a letter to multiply its value by 1,000. For example, an overlined V means 5,000 and an overlined X means 10,000. Most everyday use (years, chapter numbers, Super Bowls) stays well under 3,999, so this converter covers the full practical range.

Quick reference: common values

Roman numerals look ancient, but they show up in plenty of modern places. Knowing where they appear, and which conventions are strictly followed, takes the guesswork out of reading them. Below are the contexts you will actually run into, plus the mistakes people make most often.

Where Roman numerals still appear

• Movie and TV copyright dates: end credits often render the year in Roman numerals to make the age of a film less obvious at a glance. MMXXIV = 2024.
• Super Bowl numbering: the NFL uses Roman numerals for every game except Super Bowl 50. LIX = 59, LX = 60, LXIV = 64.
• Book structure: front matter (preface, introduction, table of contents) is usually paginated with lowercase Roman numerals (i, ii, iii, iv) before the main text switches to Arabic.
• Clock and watch faces: classic dials use I through XII. Many of them swap IV for IIII (see the next section).
• Royal and papal names: Queen Elizabeth II, King Charles III, Pope John Paul II, Louis XIV. Roman numerals disambiguate monarchs who share a first name.
• Outlines: formal outlines use I, II, III for top-level points and A, B, C below them.
• Ordinal markers: World War I, World War II, Article XIV of the U.S. Constitution.

Why clock faces often show IIII instead of IV

Walk past almost any analog clock with Roman numerals and the four-o'clock mark is probably IIII, not IV. Two reasons are cited most often. First, visual symmetry: IIII on the left mirrors the weight of VIII across the dial, so the face looks balanced. Second, a practical one: on a clock with the numerals oriented toward the center, a rotated IV can look like VI, which is already six o'clock across the face. Historians also note that early clockmakers worked from cast molds, and a set of four Is, four IIs, four IIIs, and four IIIIs could be cast more cleanly than mixing IV into the batch. Whatever the real origin, the IIII convention has stuck for centuries.

Common mistakes and how to avoid them

Year conversion shortcut

For any year up to 3,999, split the number into thousands, hundreds, tens, and ones. Convert each piece separately, then concatenate. The order is always thousands first.

• 2024: 2000 (MM) + 20 (XX) + 4 (IV) = MMXXIV
• 1776: 1000 (M) + 700 (DCC) + 70 (LXX) + 6 (VI) = MDCCLXXVI
• 1984: 1000 (M) + 900 (CM) + 80 (LXXX) + 4 (IV) = MCMLXXXIV
• 2026: 2000 (MM) + 20 (XX) + 6 (VI) = MMXXVI

This place-by-place method is how most people learn convert to roman numerals in school, and it scales to any year you are likely to write on a tattoo, wedding invitation, or cornerstone plaque.