Roman Numeral Converter: Numbers to Roman & Back

Choose Number → Roman to turn a whole number into Roman notation, or Roman → Number to decode a numeral. Results update immediately and can be copied without submitting a form or reloading the page.

The converter returns one consistent modern spelling. It uses IV, IX, XL, XC, CD, and CM where subtraction is expected and rejects inputs such as IC or VX rather than guessing what the writer intended.

Each valid result includes a token breakdown, making the page useful both as a quick converter and as a way to check how the numeral was assembled.

Modern Roman numerals are built from seven Latin letters. I represents 1, V represents 5, X represents 10, L represents 50, C represents 100, D represents 500, and M represents 1,000.

Symbols normally appear from larger to smaller values and are added. For example, MDCLXVI is 1,000 + 500 + 100 + 50 + 10 + 5 + 1, which equals 1,666.

A smaller symbol placed immediately before a permitted larger symbol forms a subtractive pair. Modern canonical notation uses six such pairs: IV, IX, XL, XC, CD, and CM.

Subtraction is local, not a general rule allowing any small symbol before any larger one. Ninety-nine is XCIX, not IC; forty-nine is XLIX, not IL.

Roman numeral usage was not completely uniform across antiquity, the medieval period, inscriptions, manuscripts, and decorative settings. Additive forms and other variants can be historically genuine even when they differ from the modern classroom convention.

This tool deliberately validates one predictable modern system. That makes conversion reversible: every accepted numeral decodes to a number, and encoding that number produces the same numeral again.

A rejected form is therefore not automatically proof that an inscription, clock, or manuscript is historically wrong. It means only that the input is outside this converter's canonical modern rules.

Use this chart for quick classroom reference or enter any value in the converter to see its construction. The pattern repeats by place value: ones use I, V, and X; tens use X, L, and C.

The chart uses canonical subtractive forms, including IV, IX, XL, XC, and compound values such as XLIX and XCIX.

The converter does not silently rewrite invalid input because several different mistakes can produce the same apparent value. It instead asks for the canonical modern spelling.

Some entries below are historically attested or common on clocks, while others are simply unsupported shortcuts. The correction column shows the form produced by this converter.

Roman numerals are still used for years on buildings and film credits, monarch and pope numbers, book sections, event editions, clock faces, and numbered outlines. The year 2026 is MMXXVI.

This tool converts one whole number at a time. To write a date, convert the day, month number, and year separately, then preserve the date order and separator required by your context.

Clock faces often display IIII for four even though IV is the canonical form returned here. That clock-face convention should not be treated as a general replacement for IV in modern number conversion.

Lowercase input is accepted and converted to uppercase before validation. Compatibility characters such as Ⅻ are also normalized, so Ⅻ is read as XII and converted to 12.

Unicode recommends ordinary Roman numerals be composed from sequences of Latin letters for most uses. The separate Number Forms characters exist mainly for compatibility and specialised layout needs.

The copied result therefore uses ordinary Latin letters such as M, C, X, and I rather than precomposed Roman numeral characters.

Using the seven ordinary symbols without additional marks, canonical place-value notation runs from I to MMMCMXCIX, or 1 to 3,999.

Larger Roman numerals have been written with overlines, apostrophus forms, additional historical symbols, and other conventions. Those systems are not represented consistently in plain text and are not interchangeable.

Rather than presenting one extension as universally standard, this converter keeps a clear boundary and reports values above 3,999 as unsupported.

The classical Roman numeral system was not a positional decimal system and has no ordinary place-holding zero equivalent to the digit 0 used today. This converter therefore begins at 1.

Negative values and decimal fractions are outside the supported notation. Historical Romans did use fractional systems in particular contexts, but they are not the same as converting a modern decimal such as 2.75 with the seven standard letters.

The tool converts notation; it does not evaluate Roman-numeral arithmetic. Convert each numeral to a number first, perform the calculation with an appropriate calculator, and convert the final supported whole-number result back if needed.