Roman Numerals Converter
Convert between Roman numerals and decimal numbers with conversion history
Converter
Numbers
Education
Mathematics
No conversion history yet.
Successfully converted numbers will appear here.
Sample Conversions
Common Numbers
1I
4IV
5V
9IX
10X
27XXVII
Larger Numbers
100C
500D
1000M
1984MCMLXXXIV
2023MMXXIII
3999MMMCMXCIX
How Roman Numerals Work
Basic Symbols
I
1
V
5
X
10
L
50
C
100
D
500
M
1000
Rules
- When a smaller numeral appears before a larger one, subtract it (IV = 4, IX = 9)
- When a smaller numeral appears after a larger one, add it (VI = 6, XI = 11)
- Only I, X, and C can be used for subtraction
- A letter can be repeated up to three times in succession (III = 3, XXX = 30)
- I can only be subtracted from V and X
- X can only be subtracted from L and C
- C can only be subtracted from D and M
History Feature
Successfully converted numbers are automatically saved to your browser's local storage. You can revisit previous conversions, compare different numbers, and manage your conversion history.
All processing happens in your browser - no data is sent to servers.
Frequently Asked Questions (FAQ)
What are Roman numerals?
Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. They use combinations of letters from the Latin alphabet: I, V, X, L, C, D, and M.
What is the range of numbers this converter supports?
This converter supports numbers from 1 to 3999. This covers the practical range of Roman numerals commonly used in historical contexts and modern applications.
How do Roman numerals work?
Roman numerals use seven basic symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Numbers are formed by combining symbols and adding the values. However, when a smaller numeral appears before a larger one, it is subtracted (e.g., IV = 4, IX = 9).
What are the subtraction rules in Roman numerals?
Only I, X, and C can be subtracted. I can be subtracted from V and X. X can be subtracted from L and C. C can be subtracted from D and M. The same letter cannot be repeated more than three times in succession.
Are my conversions processed securely?
Yes, all processing happens in your browser. No data is sent to any server, ensuring complete privacy and security.
Can I convert negative numbers or zero?
No, Roman numerals do not have symbols for zero or negative numbers. The system was designed for counting and positive integers only.
How long is the conversion history kept?
The history is stored in your browser's local storage and persists until you clear it manually or clear your browser data. We keep the last 50 successful conversions.
Can I export my conversion history?
Currently, the history is stored locally in your browser. You can copy individual conversion results using the copy buttons provided.