Decode Those Mysterious Letters on Buildings
You’re staring at a cornerstone that says MCMXLVII and wondering what year this building was built. Or a movie credits screen shows a copyright date as MMXXIV and you’re trying to work out if that’s 2024 or 2034. Roman numerals look elegant, but reading them isn’t intuitive once you get past X.
Type a decimal number (1 to 3999) and get the Roman numeral. Or type a Roman numeral and get the decimal. Both fields update as you type, it’s bidirectional and instant.
The Subtractive Notation Thing
This is where most people get confused. Normally you add symbols left to right, XVI is 10 + 5 + 1 = 16. But when a smaller symbol appears before a larger one, you subtract. IV isn’t 1 + 5, it’s 5 - 1 = 4. IX is 9. XL is 40. CD is 400. CM is 900.
That’s why 1994 is MCMXCIV and not MDCCCCLXXXXIIII. The subtractive rule keeps things compact. Here’s a quick reference:
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Enter 1994 to see MCMXCIV. Enter XLII to see 42. The converter handles everything from I to MMMCMXCIX (3999).
When You’ll Need This
Copyright dates. Film studios love Roman numerals in their copyright notices. MMXXVI looks more timeless than 2026, but it also makes half the audience squint.
Architecture and history. Old buildings, monuments, and coins use Roman numeral dates. If you’re visiting Rome (the irony), you’ll see them everywhere.
Academic outlines. Some style guides still require Roman numeral numbering for major sections: I, II, III for top-level, then A, B, C for sub-levels.
Design work. Wedding invitations, watch faces, chapter headings in books, Roman numerals carry a certain formality that Arabic numerals don’t.
Numbers above 3999 need special notation (like vinculum, a bar over the numeral to multiply by 1000) that the standard system doesn’t cover. For spelling out numbers as English words instead, the Number to Words Converter handles that.
All conversion runs in your browser, nothing gets sent anywhere.