Roman Numeral Converter
Convert between numbers and Roman numerals in either direction.
Try an example
MCMXCIV
About this calculator
What Are Roman Numerals?
Roman numerals are a number system that began in ancient Rome, using letters of the alphabet to stand for values. They stayed in everyday use long after the Roman Empire fell, until Arabic numerals (0–9) gradually replaced them around the 14th century. You still see them today on clock faces, in the numbering of book chapters and outlines, in copyright dates on film credits, on monuments, and in the names of events such as the Olympics and the Super Bowl. This converter turns ordinary numbers into Roman numerals and back, and can handle dates as well.
The Seven Symbols
- I = 1
- V = 5
- X = 10
- L = 50
- C = 100
- D = 500
- M = 1,000
Worked Example
1994 converts to MCMXCIV — built from M (1000) + CM (900) + XC (90) + IV (4), each piece chosen greedily from the largest value that still fits.
The Rules for Writing Them
- Additive principle: symbols are written from largest to smallest and added — VIII = 5 + 3 = 8, and MDC = 1,600.
- Subtractive principle: a smaller symbol placed before a larger one is subtracted — IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.
- Repetition: I, X, C and M can repeat up to three times in a row (III = 3), but V, L and D are never repeated.
- Which subtractions are allowed: I can precede V and X; X can precede L and C; C can precede D and M.
For example, 1994 is MCMXCIV: M (1,000) + CM (900) + XC (90) + IV (4).
Limits of the System
There is no symbol for zero, and the standard notation tops out at 3,999 (MMMCMXCIX). Larger numbers historically used a bar over a numeral to multiply it by 1,000, though that is rarely seen today. Because the system is hard to use for arithmetic, merchants and mathematicians eventually moved to positional Arabic numerals.
Handy Uses
Use the converter to check a movie's copyright year, to number the sections of a document correctly, to read the date on a building, or to help with homework. If you work with other number systems, the Binary Calculator and the Hex Calculator cover base 2 and base 16.
Worked example
1994 converts to MCMXCIV — built from M (1000) + CM (900) + XC (90) + IV (4).
Frequently asked questions
What's the highest number this can convert?
Standard Roman numerals go up to 3,999 (MMMCMXCIX) — beyond that, historical notation gets inconsistent (some systems used a bar over a numeral to multiply by 1,000), so this calculator caps at the standard range.
Why does my Roman numeral input get rejected?
The converter only accepts well-formed, canonical Roman numerals — non-standard forms like IIII (instead of IV) or VV aren't valid under the standard subtractive notation rules.
Why is 4 written as IV instead of IIII?
Roman numerals use subtractive notation for four of the nine values that would otherwise need 4 repeated symbols (4, 9, 40, 90, 400, 900) — placing a smaller symbol before a larger one means 'subtract,' keeping numerals shorter.
