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Tools
Roman Numerals
Convert between Arabic numbers and Roman numerals. Supports bi-directional conversion for numbers between 1-3999.
Frequently asked questions
Why is the range limited to 1–3999?
This is the most common standard for Roman numerals using I, V, X, L, C, D, and M without extra notation. Larger numbers typically require overlines or alternative conventions.
What are the basic rules for Roman numerals?
Symbols are usually written from largest to smallest and added (VIII = 8). A smaller symbol before a larger one means subtraction (IV = 4, IX = 9).
Do Roman numerals have a zero or negative numbers?
No. Classical Roman numerals represent positive integers only. If you need zero, negatives, or decimals, Arabic numbers are used.
How do I know if a Roman numeral is valid?
Valid numerals follow repetition and subtraction rules (for example, you don’t write IIV for 3). This converter checks the input and shows whether the conversion is valid.
Convert between number systems
Our calculator makes it easy to convert between Arabic numbers (1, 2, 3...) and Roman numerals (I, II, III...). Enter either an Arabic number or a Roman numeral, and you'll instantly get the result in the other system. Supports all numbers from 1 to 3999.
How Roman numerals work
Roman numerals use seven basic symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). By combining these symbols, any number up to 3999 can be expressed. A smaller symbol before a larger one means subtraction (IV = 4), while symbols in descending order are added (VI = 6).
Modern uses today
Although Roman numerals originate from ancient Rome, they are still used today in many contexts. They appear on clock faces, for numbering book chapters, for important years and events (Super Bowl LVIII), in naming royalty and popes, and in classical architecture.
Roman numerals: rules and examples
Roman numerals are an ancient number system still used today in clocks, book chapters, and events (like Super Bowl numbers).
The symbols
The most common symbols are:
I= 1V= 5X= 10L= 50C= 100D= 500M= 1000
How it works
There are two main patterns:
- Additive: symbols are added from left to right (
VIII= 5 + 3 = 8). - Subtractive: a smaller symbol before a larger one means subtraction (
IV= 4,IX= 9).
Typical subtractive pairs include:
IV(4),IX(9)XL(40),XC(90)CD(400),CM(900)
Common mistakes
- Writing
IIIIfor 4 (often seen on clocks, butIVis the standard form). - Mixing subtractive rules too freely.
- Using zero: Roman numerals do not have a standard symbol for 0.
Using the converter
- Enter a number to get the Roman numeral.
- Or enter a Roman numeral to convert back.
If your input contains unusual characters or non-standard patterns, the result may differ from what you expect.
How to read this calculator
These results are meant as guidance. They are based on rules, assumptions, and simplified models that can differ from your exact real-world situation.
Methodology
Each calculator uses defined inputs, assumptions, and logic. We explain the broader approach on the methodology page.
Read methodologySources and updates
Important calculators should be traceable back to official rules, public guidance, or other clearly stated references.
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