🏛️ Roman Numeral Converter

Roman numerals are the number system used in ancient Rome, representing values using combinations of the Latin letters I, V, X, L, C, D, and M. The system spread across Europe along with the Roman Empire and remained the standard way of writing numbers in medieval Europe for centuries. Today, everyday arithmetic uses Arabic numerals, but Roman numerals are still widely used wherever tradition or formality matters — clock faces, book chapters, film production years, and regnal numbers for monarchs and popes (such as Elizabeth II).

Roman numerals normally follow additive notation, listing symbols from largest to smallest and adding their values. Example: VI = 5 + 1 = 6.

However, when a smaller-value symbol appears before a larger one, it is subtracted instead — this is subtractive notation. Example: IV = 5 − 1 = 4, IX = 10 − 1 = 9, XL = 40, XC = 90, CD = 400, CM = 900.

The same symbol may not repeat more than three times in a row (III = 3 is valid, but IIII = 4 is not — IV is the correct form).

Standard Roman numerals, which repeat M (1,000) up to three times, can only express numbers up to 3,999. To go beyond that, an ancient convention places a vinculum (overline) over a group of symbols to indicate the value is multiplied by 1,000.

For example, 4,000 is written as IV with an overline (4 × 1,000), and 5,000 as V with an overline. This calculator splits your number into thousands and remainder, converts the thousands portion into an overlined Roman numeral, and appends the remainder in standard notation — supporting values up to 3,999,999.

Years frequently seen in film credits, cornerstones, and monuments convert to Roman numerals as follows.

Frequent errors when reading or writing Roman numerals include:
• Repeating a symbol four times, like IIII — the correct form is IV.
• Subtracting across more than one step, like VX or IL — subtraction only works between adjacent tiers (I only before V or X; X only before L or C, and so on).
• Writing the same symbol more than three times in a row instead of switching to subtractive notation.
• Assuming there is a Roman numeral for zero — there is none.

• Analog and wristwatch clock faces
• Copyright/production years in film and TV credits
• Prefatory page numbers in books and papers
• Super Bowl and Olympic Games editions
• Regnal numbers for monarchs and popes (e.g., Elizabeth II, John Paul II)
• Cornerstones and monument inscriptions marking a construction year