How to Convert Numbers to Roman Numerals
Roman numerals originated in ancient Rome and remained the standard way of writing numbers in Europe for centuries. You can still see them today on clock faces, in book chapter headings, and in the names of monarchs and popes. I built this converter to be a simple tool for translating between our modern Arabic numerals and this classic system.
The Basic Symbols
The Roman numeral system uses seven basic letters from the Latin alphabet to represent numbers:
- I = 1
- V = 5
- X = 10
- L = 50
- C = 100
- D = 500
- M = 1000
How Numbers are Formed
Numbers are formed by combining these symbols and adding or subtracting their values based on a few key rules:
- Addition: When symbols are placed from left to right in order of value from largest to smallest, their values are added. For example, VI is 5 + 1 = 6, and LXX is 50 + 10 + 10 = 70.
- Subtraction: A smaller numeral placed *before* a larger one is subtracted from the larger numeral. This is used to form certain numbers more efficiently. For example, instead of writing IIII for 4, it is written as IV (5 - 1). This rule only applies to specific pairs: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900).
- Repetition: A symbol can be repeated up to three times in a row to multiply its value. For example, III is 3, and XXX is 30. The symbols V, L, and D are never repeated.
This converter handles all these rules for you, allowing for quick and accurate translations up to the number 3999, which is the largest number that can be conventionally written in Roman numerals (MMMCMXCIX).