Roman numeral converter
Convert an Arabic number to Roman numerals (2026 → MMXXVI) or Roman to Arabic. Supports 1–3999 and validates the notation. Everything runs in your browser.
= –
= –
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
FAQ
What range is supported?
The classic notation 1 to 3999 (MMMCMXCIX). Larger numbers use an overline, which plain text cannot represent.
Why does it say “invalid” for a Roman numeral?
The notation breaks the rules – e.g. IIII instead of IV, VX, or repeated V, L, D. Only the standard (canonical) form is accepted.
Where are Roman numerals used?
Years, monarchs and popes (Charles IV), book chapters, clock faces or centuries (21st century = XXI).