Roman Numerals Calculator — Roman-Arabic Converter

Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. A value is formed by adding symbols from largest to smallest, e.g. MMXXIV = 2024. Symbols of the same value repeat at most three times in a row.

When a smaller symbol precedes a larger one, its value is subtracted. Instead of IIII we write IV (4), and instead of VIIII — IX (9). The rule applies to the pairs IV, IX, XL, XC, CD and CM and shortens the notation.

Classic notation has no symbol larger than M (1000). The largest number written with at most three M is MMMCMXCIX = 3999. Numbers above require special markings that this calculator does not support.

The Roman system arose as additive notation and needed no zero. Zero as a number appeared later in the positional system. There is no symbol for zero in Roman notation, so the calculator handles values from 1 upward.

You see them on clock faces, in chapter and volume numbering, theatre acts, ruler names, century markers (21st century), Olympic games and floors. They serve a decorative and ordinal role.

The year 1984 is MCMLXXXIV: M (1000) + CM (900) + L (50) + XXX (30) + IV (4) = 1984. It combines the additive rule (XXX, L) with the subtractive rule (CM, IV) in one number.

Yes. The calculator converts text to uppercase before conversion, so "mmxxiv" and "MMXXIV" give the same result, 2024. Characters outside I, V, X, L, C, D, M are treated as invalid and yield 0.

If characters other than I, V, X, L, C, D, M appear (e.g. the letter A or a digit), the calculator returns 0. It parses characters by value but does not verify full notation correctness — keep the symbol order right.

Select "Arabic to Roman" to convert a regular number (e.g. 2024) to Roman notation, or "Roman to Arabic" to read a Roman numeral (e.g. MMXXIV) as a decimal value. The calculator uses the appropriate field.

In its classic form, each number 1–3999 maps to exactly one correct Roman string. Historical variants existed (e.g. IIII on clocks), but this calculator always generates the classic form with the subtractive rule.