Roman Numeral Converter – Number to Roman Numerals Online Free
The Roman Numeral Converter is a free online tool that instantly converts numbers to Roman numerals and Roman numerals back to numbers. It supports numbers from 1 to 3,999,999 (using vinculum/overline notation for values above 3,999), includes a batch converter for up to 100 values, quick-click examples, and a full reference table for symbols and subtractive notation. All conversion happens in your browser.
How to Convert Roman Numerals Online
- 01
Choose conversion direction
Use the toggle to select "Number → Roman" (default) or "Roman → Number". The input field and result panel update accordingly.
- 02
Enter your value
Type a number between 1 and 3,999,999, or type Roman numerals. The result appears instantly below the input — no button to press.
- 03
Copy or convert in batch
Click the copy icon to copy the result. For multiple values, open the batch converter to paste up to 100 numbers and download the results.
Features
- ✓Instant number-to-Roman and Roman-to-number conversion
- ✓Supports 1 to 3,999,999 (vinculum notation for 4,000+)
- ✓Round-trip validation for Roman numeral input
- ✓Batch converter: up to 100 numbers at once
- ✓Download batch results as .txt
- ✓Current year displayed in Roman numerals
- ✓Quick example buttons for common values
- ✓Full symbol reference table (I, V, X, L, C, D, M)
- ✓Subtractive notation table (IV, IX, XL, XC, CD, CM)
- ✓100% browser-based — no server, no login
Frequently Asked Questions
How do I convert a number to Roman numerals?
Select the "Number → Roman" mode (selected by default), type your number in the input field, and the Roman numeral equivalent appears instantly below. Numbers from 1 to 3,999 use standard Roman notation (I, V, X, L, C, D, M). Numbers from 4,000 to 3,999,999 use vinculum notation with an overline bar (e.g. V̄ = 5,000).
How do I convert Roman numerals to a number?
Click the "Roman → Number" tab, type or paste your Roman numerals (uppercase or lowercase), and the decimal number appears instantly. The converter validates the input using a round-trip check — it converts to a number and then back to Roman numerals to verify the result is canonical.
What is the maximum number supported?
The converter supports numbers from 1 to 3,999,999. Numbers above 3,999 use vinculum notation (a bar over the symbol to multiply it by 1,000). For example, V̄ = 5,000, X̄ = 10,000, M̄ = 1,000,000. The reverse converter (Roman → Number) only supports standard notation up to 3,999.
What are subtractive Roman numerals?
Subtractive notation is a rule in Roman numerals where a smaller value placed before a larger one means subtraction. For example: IV = 4 (5−1), IX = 9 (10−1), XL = 40, XC = 90, CD = 400, CM = 900. This avoids writing IIII for 4 or VIIII for 9.
How does the batch converter work?
Click "Batch converter" to expand the panel. Enter one number per line (up to 100 numbers, each between 1 and 3,999). The results appear immediately on the right. You can copy all results to the clipboard or download them as a .txt file.