Roman Numeral Calculator

The Roman Numeral Calculator lets you convert numbers to and from Roman numerals instantly. Just paste a number like 42 or a Roman numeral like XLII, and the result updates live. It works both directions decimal to Roman, or Roman to decimal and you can switch modes easily using the options.

It’s handy for homework, history, or any time you need to decode or encode Roman numerals quickly. You’ll get real-time feedback as you type, and the output flashes to let you know it’s working. You can customize the output too choose whether you want uppercase Roman letters, whether to apply subtractive notation (like IV for 4), and whether to skip blank lines.

Everything works directly in your browser no reloads, no lag, no nonsense.

How to Use:

1. Enter Input
   Type or paste a list of Roman numerals (e.g. X, MMXXIV) or decimal numbers (1, 2024) into the input box.
2. Choose Conversion Mode
   Use the radio buttons to select:
   • To Roman converts decimal numbers into Roman numerals
   • To Decimal converts Roman numerals to standard numbers
3. Use Toggles to Customize
   • Uppercase: Converts Roman output to uppercase (XIV) or lowercase (xiv)
   • Use subtractive notation: Enables compact forms like IV instead of IIII
   • Trim empty lines: Ignores blank lines in input
4. View Output Instantly
   The output updates live with every change. It flashes blue briefly to confirm it’s refreshed.
5. Use the Buttons
   • Convert: Manually re-trigger conversion
   • Copy Output: Copies result to clipboard

What Roman Numeral Calculator can do:

This tool converts single values or entire lists from decimal to Roman numerals or vice versa. It’s perfect for checking school assignments, formatting numbers for events or clocks, or decoding ancient inscriptions. It supports values up to 3999, applies subtractive rules if needed, and lets you control how Roman output is formatted. You can clean up spacing, copy results, and even export your conversion with one click.

Example:

Input (To Roman mode):

4
9
25
2024

Output:

IV  
IX  
XXV  
MMXXIV

Roman Numeral Calculator Table:

This table shows common numbers and their Roman numeral equivalents. It includes small numbers, round values, and large figures often seen in outlines, dates, or classical references. Ideal for checking conversions or building readable labels.

Common Use Cases:

Use it for converting modern numbers to Roman for movie titles, year stamps, or historical documents. Flip it around to decode Roman numerals into numbers for data entry, trivia, or research. It’s also great for teachers and students working with ancient numeral systems in math or history class.