Online converter of Roman numerals to Arabic and vice versa
Convert Roman numerals to Arabic and vice versa. Process multiple numbers line by line with instant results and a detailed reference.
Convert to Roman Numerals
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Features of the "Roman to Arabic Converter"
Roman to Arabic Conversion
Instantly converts Roman numerals to their Arabic representation. Useful for understanding classical numeral systems and historical documents.
Arabic to Roman Conversion
Converts Arabic numbers to Roman numerals. Essential for educational purposes and working with classical texts.
Multiple Number Processing
Processes multiple numbers at once by entering them line by line. Saves time when working with large sets of numbers.
Guide & Usage Details
Rules for Writing Roman Numerals
Roman numerals are a system of writing numbers using the symbols I, V, X, L, C, D, M, where values are added or subtracted depending on their position.
Basic rules:
Roman numerals are formed using the symbols I, V, X, L, C, D, M
Numbers are written from left to right, usually from largest to smallest, except in subtraction cases
The symbols I, X, C, M can be repeated no more than three times in a row
If a smaller value appears before a larger one, it is subtracted (IV = 4, IX = 9)
If a smaller value appears after a larger one, it is added (VI = 6, XI = 11)
Subtraction is only allowed with adjacent ranks: I can subtract from V and X; X can subtract from L and C; C can subtract from D and M
The symbols V, L, D are never repeated
Roman numerals do not include zero or negative numbers
Maximum standard value: 3999 (MMMCMXCIX)
The classical Roman system does not define a standard way to represent numbers above 3999 without additional notation (e.g., overlines to indicate thousands).
Basic Roman Numerals
Roman Numeral | Arabic Number | Type |
|---|---|---|
I | 1 | Base |
V | 5 | Half |
X | 10 | Base |
L | 50 | Half |
C | 100 | Base |
D | 500 | Half |
M | 1000 | Base |
Conversion Rules
The algorithm is applied sequentially to each symbol in the string:
read from left to right
if the current symbol is smaller than the next → subtract
otherwise → add
Conversion Examples
Roman Numeral | Arabic Number |
|---|---|
IV | 4 |
IX | 9 |
XL | 40 |
XC | 90 |
CD | 400 |
CM | 900 |
Example Converting a Complex Number
Example: converting the number 1984
Result: 1000 (M) + 900 (CM) + 80 (LXXX) + 4 (IV) = MCMLXXXIV
Common Mistakes
Violating the “rule of three”
Incorrect symbol order
Using invalid combinations
Examples of Errors
Arabic Number | Incorrect | Correct | Reason |
|---|---|---|---|
4 | IIII | IV | Rule of three |
10 | VV | X | V cannot be repeated |
49 | IL | XLIX | Invalid subtraction |
99 | IC | XCIX | Invalid subtraction |
Tool Description
Convert Roman numerals to Arabic and vice versa with our online converter. Process multiple numbers line by line with instant results and a detailed reference guide.
The tool supports both conversion from Roman to Arabic numerals and from Arabic to Roman, making it useful for historians, students, and anyone working with classical numeral systems.
Perfect for educational purposes, historical research, and understanding classical number representations with built-in reference information.
Frequently Asked Questions (FAQ)
The Roman and Arabic numeral converter allows you to convert numbers between the Roman and Arabic numeral systems. This is useful for historians, students studying classical texts, and anyone working with ancient documents.
Roman numerals use letters to represent values: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Numbers are written from left to right from largest to smallest. If a smaller number precedes a larger one, it is subtracted (IV=4, IX=9).
The converter supports Arabic numerals from 1 to 3999 and their corresponding Roman numerals. The maximum Roman numeral is MMMCMXCIX (3999). There is no zero in the Roman system.
Yes, you can enter multiple numbers, each on a new line, and the tool will process them all at once. This is convenient for batch processing of large lists of numbers.
Roman numerals are used for numbering chapters in books, denoting centuries, on clock faces, and in various official documents and inscriptions.
The concept of zero as a number and placeholder was developed much later than the creation of the Roman numeral system, which was primarily additive and subtractive, not positional like the Arabic system.
Yes, while there are historical variations, the most common form today is 'modern Roman notation,' which follows specific rules for subtractions (e.g., IV for 4, IX for 9) and for avoiding repeating a symbol more than three times.
The traditional Roman system does not have a standard way to represent numbers greater than 3999.
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