Roman Numeral - Online Roman Number Conversion

Convert Roman numbers

Decimal number

Enter a number from 1 to 3999

Roman Number

Reference table

Roman Numeral Converter - Accurate Free Online Roman Numeral Converter

Free online Roman numerals conversion tool from Tan Phat Digital. 2-way conversion: decimal numbers (Arabic) to Roman numbers and vice versa. Supports numbers from 1 to 3999 (I to MMMCMXCIX). Validate Roman numbers - detect wrong format. Reference table of 20 common numbers with one click. Copy results quickly. Explanation of Roman numeral rules in detail. Useful for students, designers, writers, and anyone who needs to work with Roman numbers in clocks, outlines, copyright, king/emperor names, Super Bowl, and many other applications.

Outstanding features

2-way conversion: Decimal ↔ Roman
Supports numbers from 1 to 3999
Validate Roman numbers - detect incorrect format
Show detailed error if input is invalid
Reference table of 20 popular numbers
Click the number in the table to quickly convert
Copy results with one click
Realtime conversion when typing
Supports both uppercase and lowercase input
Explain the Roman numeral rule
Simple interface, easy to use
Offline processing in the browser
Completely free

What are Roman numbers and where are they used?

Roman numerals is a number system used in ancient Rome, using Latin letters to represent numbers: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Today Roman numbers are still widely used: Clocks: Many analog watches use Roman numbers (I-XII). Outline/Table of Contents: I, II, III for chapters, A, B, C for sections. Copyright year: © MMXXIV (2024) looks more elegant. Names of kings/emperors: Louis XIV, Elizabeth II, Pope John Paul II. Super Bowl: Super Bowl LVIII (58). Movie/Book: Episode IV, Volume III, Part II. Architecture: Five built on ancient building. This tool helps you convert quickly without having to remember complicated rules.

Benefits when used

  • •Convert quickly and accurately
  • •No need to remember complicated rules
  • •Learn Roman numerals through practice
  • •Validate input - avoid errors
  • •Convenient reference table
  • •Useful for many purposes
  • •Unlimited free

How to convert Roman numbers

  1. 1To convert Decimal → Roman: Enter the decimal number (1-3999) in the left box
  2. 2To convert Roman → Decimal: Enter the Roman number in the right box
  3. 3The results are automatically displayed in the remaining box
  4. 4If the input is invalid, the error message
  5. 5will be displayed Click on the number in the reference table to quickly convert
  6. 6Click the Copy button to copy the

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