How to Use the Roman Numeral Converter
This tool provides instant, two-way conversion between standard (Arabic) numerals and Roman numerals.
- 1. Number to Roman: Simply start typing a number between 1 and 3999 in the first box. The Roman numeral equivalent will appear in the second box automatically as you type.
- 2. Roman to Number: Alternatively, type a valid Roman numeral (e.g., MMXXV) in the second box. The corresponding standard number will appear in the first box.
- 3. Instant and Two-Way: The conversion happens in real-time. Typing in either box will update the other, and clearing one box will clear both.
Frequently Asked Questions
What are the basic Roman numerals?
The system is based on seven core symbols:
- I = 1
- V = 5
- X = 10
- L = 50
- C = 100
- D = 500
- M = 1000
What is the subtractive principle?
Typically, Roman numerals are written from largest to smallest (e.g., XVI = 16). However, to avoid repeating a symbol four times (like IIII), a subtractive principle is used. Placing a smaller numeral before a larger one means you subtract the smaller value. For example:
- IV = 4 (5 - 1)
- IX = 9 (10 - 1)
- XL = 40 (50 - 10)
- XC = 90 (100 - 10)
- CD = 400 (500 - 100)
- CM = 900 (1000 - 100)
Why does the calculator stop at 3999?
Standard Roman numeral notation does not have a native way to represent numbers of 4000 or greater. The largest number that can be written using standard symbols is 3999 (MMMCMXCIX). While ancient Romans used other methods for larger numbers (like a bar over the top, called a vinculum, to multiply by 1000), these are not part of the standard system this calculator uses.