Roman Numeral Converter

What Roman numerals are, and why they still show up

Roman numerals are a number system the Romans used for roughly two thousand years before Europe switched to Hindu-Arabic digits in the late Middle Ages. The switch happened because the new digits were easier for arithmetic — try multiplying XXVII by LXIV without a calculator and you'll see the problem. But Roman numerals stuck around for ceremonial and decorative work, and they still show up in places you encounter every week: Super Bowl titles (Super Bowl LIX was 2025), movie copyright years in the closing credits, book chapter numbers, monarch names (Elizabeth II, Louis XIV), watch faces, and the year carved into the cornerstone of every government building.

The Roman Numeral Converter on this page goes both directions. Type a regular number from 1 to 3999, get the Roman numeral. Type a Roman numeral, get the regular number. The two fields are independent — both live, no Convert button to press, no signup. If you mistyped your input, the result simply updates. The whole experience is supposed to feel like asking a friend who happens to remember the rules.

The seven letters

Roman numerals use seven letters, each with a fixed value:

Every Roman numeral is built by writing some combination of these letters from left to right. Larger values go first; smaller values follow. To write 17, you stack X (10) + V (5) + I + I (1 + 1) and get XVII. To write 152, you write C + L + I + I and get CLII. The values add up — most of the time.

The Romans had no symbol for zero. They also had no fractions in the modern sense, no negative numbers, and no easy way to represent numbers larger than a few thousand. The standard system tops out at 3999 (MMMCMXCIX), which is why our converter caps inputs there. There are extensions involving overlines (a bar over a letter multiplied its value by 1000), but those are non-standard and rarely seen outside historical inscriptions.

The subtractive rule

If Romans had only used addition, the number 9 would have been written VIIII — V plus four I's. Some early inscriptions did exactly that, and you'll still see IIII on some clock faces today. But the standard rule that emerged in the Middle Ages introduced a shortcut: a smaller value placed before a larger value is subtracted instead of added.

The allowed subtractive pairs are:

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

You can't subtract just any letter from any other. Only I, X, and C are used as subtractors, and each can only precede the next two larger values (I before V or X, X before L or C, C before D or M). VL is not valid for 45 — the correct form is XLV (40 + 5). IC is not valid for 99 — the correct form is XCIX (90 + 9). The converter follows these rules strictly when generating output.

Converting numbers to Roman numerals

The algorithm is simple: greedy subtraction. Take your number, find the largest Roman value that fits inside it, write down that letter (or two-letter pair), subtract the value, and repeat with what's left. Stop when you hit zero.

Worked example: convert 1994 to Roman numerals.

• 1994 ÷ M (1000) → write M, remainder 994
• 994 ÷ CM (900) → write CM, remainder 94
• 94 ÷ XC (90) → write XC, remainder 4
• 4 ÷ IV (4) → write IV, remainder 0

So 1994 in Roman numerals is MCMXCIV. Sum it back the long way: 1000 + (1000 − 100) + (100 − 10) + (5 − 1) = 1000 + 900 + 90 + 4 = 1994. The numerals match.

That MCMXCIV is the number Quentin Tarantino's Pulp Fiction shows in its closing credits, since it was released in 1994. Movies dropped this convention around the 2000s for legibility reasons, but you'll still find it in older films and reruns.

Converting Roman numerals to numbers

Going the other direction works left to right, one letter at a time. At each position, look at the current letter and the next letter. If the current letter's value is less than the next letter's value, subtract; otherwise add. Sum the running total until you reach the end.

Worked example: convert MCMLXXVII to a number.

• M (1000), next is C (100). 1000 ≥ 100, so add 1000. Total: 1000.
• C (100), next is M (1000). 100 < 1000, so subtract: −100 + 1000 = +900. Total: 1900. Skip the M (consumed).
• L (50), next is X (10). 50 ≥ 10, so add 50. Total: 1950.
• X (10), next is X (10). 10 ≥ 10, so add 10. Total: 1960.
• X (10), next is V (5). 10 ≥ 5, so add 10. Total: 1970.
• V (5), next is I (1). 5 ≥ 1, so add 5. Total: 1975.
• I (1), next is I (1). Add 1. Total: 1976.
• I (1), no next letter. Add 1. Total: 1977.

MCMLXXVII is the year 1977. Roman numeral years on buildings are read this way every day, even if most people doing it have memorized the patterns rather than walking the algorithm.

Year reference table

Years from movies and copyrights are the single most common reason people need a Roman numeral converter. Here's the recent decade plus some round numbers:

Notice MMXXVI ("two thousand twenty-six") is six letters, while MCMXCVIII ("nineteen ninety-eight") needs nine. The 2000s are easy on Roman numerals; the late 1900s were not. Movies released between 1990 and 1999 had some of the longest year credits ever cut into a final frame.

Why no zero, and other historical gaps

The Roman numeral system isn't great at math. There's no zero, which makes positional arithmetic impossible — you can't write a "10s column" the way decimal does. There are no fractions in the modern sense (the Romans used a separate duodecimal system with names like "uncia" for twelfths). There's no easy way to write numbers larger than a few thousand without invented extensions. Multiplication and division are excruciating by hand.

That's why Europe adopted Hindu-Arabic numerals in the 13th century after Fibonacci's Liber Abaci spread the system from Islamic North Africa. Once you can write 0 through 9 and use positional notation, you can do arithmetic mechanically — the same algorithms a calculator uses. Roman numerals survived in ceremonial use precisely because they look weighty and traditional on a building or a movie poster. They were never going to come back as a primary number system.

There's a small charm in that. Roman numerals are decorative numbers — the gold leaf of the numeric world. They mark the things we want to feel permanent: cornerstones, monarchs, championships. If you needed to do your taxes in Roman numerals, you'd switch back to digits in a week. But on a watch face at midnight, XII does something IV can never quite match.

Related conversions

Roman numerals are one of several number-format conversions you might need:

• Number to Words — spells numbers out as English text ("one thousand two hundred thirty-four"). Useful for cheque-writing and legal documents.
• Binary to Decimal — converts between base 2 and base 10. The system that powers the device you're reading this on.
• Number Base Converter — handles arbitrary base conversions from 2 through 36, including the common pairs (binary, octal, decimal, hex).

Frequently asked questions

What's the largest number you can write in Roman numerals?

In the standard system, 3999 (MMMCMXCIX). The rule that no letter repeats more than three times in a row caps M at MMM (3000), and after CM (900) and XC (90) and IX (9), you've reached the maximum without extensions. Some historical systems used a bar over a letter to multiply by 1000 (so an overlined V meant 5000), but those aren't standardized and aren't supported by most converters.

Why is IIII used on clock faces instead of IV?

Mostly tradition and visual balance. On a clock face with VIII opposite IIII, the two numerals have similar visual weight; if you used IV instead, the left side of the dial would look thinner than the right. The IIII convention also predates the strict subtractive rule, so older clocks used what was historically more common. The rule itself wasn't fully standardized until the late Middle Ages.

Why no zero?

The concept of zero as a number — not just "nothing" but a placeholder you can do arithmetic with — was a later invention, coming through India and the Islamic world to Europe in the 12th and 13th centuries. The Roman system was built around counting concrete things (sheep, soldiers, coins), and "zero sheep" was just "no sheep" rather than a number. The absence of zero is one of the reasons Roman numerals can't do positional arithmetic.

Are Roman numerals case-sensitive?

Traditionally Roman numerals are written in uppercase: MCMXCIV. Lowercase forms (mcmxciv) are used in some contexts — typically for outline lists ("section i, ii, iii"), book page numbering for prefaces, or certain academic citations. The numeric value is the same. The converter on this page accepts both and normalizes input to uppercase.

What does the year 2026 look like in Roman numerals?

MMXXVI. Two thousand (MM) plus twenty (XX) plus six (VI). Six letters total, which is one of the friendlier years of the decade. The 2030s will be shorter still — 2030 is just MMXXX.

What does Super Bowl LX mean?

The NFL has used Roman numerals to number Super Bowls since 1971 (Super Bowl V), partly because the championship year doesn't match the calendar year and they wanted a clean identifier. LX is 60, so Super Bowl LX is the 60th championship, played in February 2026. Super Bowl 50 (2016) was the exception that broke the streak — the league used "50" instead of "L" because the single letter looked off on its own.

Can the converter handle negative numbers or zero?

No. Roman numerals don't represent zero or negative values. The number-to-Roman field accepts integers from 1 to 3999. Entering 0 or a negative number returns an out-of-range message.