Roman Numeral Converter

Convert any number from 1 to 3,999,999 into Roman numerals, or translate Roman numerals back into decimal numbers. The tool supports overline (vinculum) notation for large values and explains each conversion step by step.

Conversion Mode

Number → Roman Numeral Roman Numeral → Number

Enter a Number (1 – 3,999,999)

Roman Numeral
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Conversion Breakdown

Enter a value to see the breakdown.

What is a Roman Numeral Converter?

A Roman numeral converter is a tool that translates between the modern decimal number system we use every day and the ancient Roman numeral system that uses letters of the Latin alphabet. The converter works in both directions: type a decimal number to receive its Roman numeral equivalent, or type a Roman numeral to decode it into a decimal value. This makes it useful for students, historians, puzzle solvers, and anyone curious about how classical numbering works.

Roman numerals originated in ancient Rome and dominated European mathematics, commerce, and record-keeping for over a thousand years before being gradually replaced by the more efficient Hindu-Arabic decimal system during the late Middle Ages. Despite their obsolescence for arithmetic, Roman numerals remain culturally significant. You will find them on clock faces, in the copyright dates of films and television shows, on the cornerstones of buildings, in book prefaces, on coin inscriptions, and in the names of monarchs, popes, and the Olympic Games.

The system uses seven basic symbols with fixed values: I for 1, V for 5, X for 10, L for 50, C for 100, D for 500, and M for 1,000. Numbers are formed by combining these symbols additively, with a subtractive convention that places a smaller symbol before a larger one to indicate subtraction. This convention keeps the written forms compact, so 4 is written as IV rather than IIII, and 90 is written as XC rather than LXXXX.

For numbers above 3,999, the basic symbols are insufficient because Roman numerals do not include a symbol for 5,000 or 10,000 in everyday use. The classical solution is the vinculum, a horizontal line drawn above a symbol to multiply its value by 1,000. An overlined V represents 5,000, an overlined X represents 10,000, and an overlined M represents 1,000,000. This converter uses the vinculum to support values up to 3,999,999, covering virtually every practical need.

How Roman Numeral Conversion Works

Converting a number to a Roman numeral uses a greedy algorithm: at each step, subtract the largest representable value and append its symbol. Converting a Roman numeral to a number scans left to right, adding values when a symbol is at least as large as the next and subtracting when it is smaller.

Formula Symbol-value mapping with subtractive notation; overline multiplies a symbol by 1,000

Example

Convert 2025 to Roman numerals:

2025 − 1000 (M) = 1025 → "M"

1025 − 1000 (M) = 25 → "MM"

25 − 10 (X) = 15 → "MMX"

15 − 10 (X) = 5 → "MMXX"

5 − 5 (V) = 0 → "MMXXV"

Decode "MCMXC": M(1000) + CM(900) + XC(90) = 1990

How to Use This Roman Numeral Converter

Select a mode: Choose "Number → Roman Numeral" or "Roman Numeral → Number" using the radio buttons.
Enter your input: Type a whole number from 1 to 3,999,999, or a Roman numeral string using I, V, X, L, C, D, M (and overlined letters for large values).
Read the result: The converted value appears immediately in the highlighted result box, with a serif font to evoke classical inscriptions.
Review the breakdown: The conversion breakdown shows step-by-step how the answer was computed, helping you learn the system as you use it.
Copy if needed: Use the Copy Result button to place the answer on your clipboard for use in documents, presentations, or messages.

Roman Numeral Reference Chart

The table below lists every basic symbol along with its decimal value.

Symbol	Value	Notes
I	1	Originated as a single stroke or finger
V	5	Represents the shape of an outstretched hand
X	10	Two crossed hands or strokes
L	50	Originally half of a hundred symbol
C	100	From centum, the Latin word for hundred
D	500	Half of the original thousand symbol
M	1,000	From mille, the Latin word for thousand
V̅	5,000	V with overline (vinculum)
X̅	10,000	X with overline (vinculum)
L̅	50,000	L with overline (vinculum)
C̅	100,000	C with overline (vinculum)
D̅	500,000	D with overline (vinculum)
M̅	1,000,000	M with overline (vinculum)

Frequently Asked Questions About Roman Numerals

What are Roman numerals and where do they come from?

Roman numerals are a numeral system originating in ancient Rome that uses combinations of letters from the Latin alphabet to represent values. The seven basic symbols are I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). The system was the standard way of writing numbers throughout Europe for centuries and remains in use for clocks, dates, outlines, and ceremonial numbering.

How does subtractive notation work in Roman numerals?

Subtractive notation places a smaller symbol before a larger one to indicate subtraction. For example, IV means 5 minus 1, or 4, and IX means 10 minus 1, or 9. This convention avoids four repeated symbols in a row. The allowed subtractive pairs are IV, IX, XL, XC, CD, and CM. Without subtractive notation, 4 would be written IIII instead of the standard IV.

How are numbers above 3,999 represented?

Standard Roman numerals cannot express 4,000 or higher using only the seven basic symbols, because no symbol larger than M (1,000) exists. To extend the range, an overline (vinculum) is drawn above a symbol to multiply its value by 1,000. So V with an overline equals 5,000, X equals 10,000, and M equals 1,000,000, allowing values up to 3,999,999.

Why do some clocks show IIII instead of IV for 4?

Many traditional clock faces use IIII instead of IV for the number 4. This practice dates back centuries and may have aesthetic, historical, or religious reasons. Some say it balances the visual symmetry of the dial, others attribute it to a preference of King Louis XIV of France, and others suggest it avoided invoking the name of the Roman god Jupiter (IVPPITER). The convention persists on clocks to this day.

Can I convert very large numbers like a million?

Yes. This converter supports values from 1 up to 3,999,999. To express one million, the tool uses an M with an overline, which represents 1,000 times 1,000. Two million is two overlined M characters, and so on. The same subtractive rules apply at every scale, so 4,000,000 would be written as an overlined IV.

How do I read a complex Roman numeral like MCMLXXXIV?

Read Roman numerals from left to right, adding values when a symbol is greater than or equal to the next, and subtracting when it is smaller. In MCMLXXXIV: M is 1,000; CM is 900 (1,000 minus 100); LXXX is 80 (50 plus 30); IV is 4. Adding them gives 1,000 + 900 + 80 + 4 = 1,984. Breaking the numeral into chunks makes interpretation much easier.