What is Roman Numeral Converter?

Convert between Roman numerals and decimal numbers instantly. Standard mode covers 1 to 3,999 with proper subtractive notation; switch on Extended mode to handle values up to 3,999,999 using vinculum (overline) notation. The Date tab formats a calendar date as Roman numerals, which is handy for tattoos, jewelry, and dedications. The Batch tab converts a whole list of values at once.

The converter validates Roman numerals strictly: repeated subtractive pairs like IIII or VV are rejected because they're not classical form. Each symbol breakdown shows which subtractive groupings the parser used (CM = 900, IV = 4), so you can see exactly how the number is constructed. In Extended mode, type an underscore before letters or use the combining overline (V̄) to multiply by 1,000 — _V = 5,000, V̄MMXXIV = 7,024. The Date tab lets you pick month, day, and year separately and choose the order (MM.DD.YYYY, DD.MM.YYYY, or YYYY.MM.DD) plus a separator character. The Batch tab accepts one value per line, auto-detects which direction to convert each row, and lets you copy every result with a single click.

How to use

1. Enter a decimal number (1–3999) or type a Roman numeral (e.g., MCMXCIV).
2. The conversion happens instantly. See the result and a per-symbol breakdown.
3. Copy the converted value or view the reference chart for all Roman numeral symbols.

When to use

• Decoding the copyright year MCMXCVIII on an older film or book.
• Writing chapter numbers, sequel titles, or watch-face graphics in classical notation.
• Helping a student check homework while learning subtractive notation rules.

Result

Type 2024 → MMXXIV (M+M+X+X+IV). Type MCMXCIV → 1994 (M=1000, CM=900, XC=90, IV=4).

FAQ

Why is the maximum 3,999 and not larger?

Standard Roman numerals stop at M (1000), so the largest representable number using only the seven base symbols is MMMCMXCIX = 3,999. To go further, switch on Extended mode: an overline (vinculum) multiplies a symbol's value by 1,000, so V̄ = 5,000 and M̄ = 1,000,000. Extended mode tops out at 3,999,999. You can type the overline directly or use an underscore prefix like _V as a keyboard-friendly substitute.

Why does the converter reject IIII for the number 4?

Classical Roman notation uses subtractive form: 4 is IV, not IIII. While clock faces sometimes use IIII for aesthetic balance, the converter follows the standard ISO rule where each symbol repeats at most three times in a row.

Is zero a valid Roman numeral?

Romans had no symbol for zero. Medieval scholars later wrote nulla or used the letter N, but neither is part of classical Roman numeral notation. The converter starts at 1 = I.

What does the symbol breakdown show?

Each row in the breakdown shows one symbol or subtractive pair and its value. For MCMXCIV the parser produces M=1000, CM=900, XC=90, IV=4. This makes it clear that CM and XC are read as single subtractive groups, not as C-M or X-C.

Can I use lowercase letters like mcm?

Yes. The input is case-insensitive, so mcm, McM, and MCM all convert to 1900. Output defaults to uppercase, the standard inscriptional form, but you can flip the Letter case switch to lowercase for chapter headings, footnotes, or manuscript-style numerals.

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