Roman numeral converter
Convert Arabic numbers to Roman numerals and Roman numerals to Arabic numbers instantly. Supports 1 to 3999 with real-time validation.
- 100% free
- No sign-up
- No limits
- Instant results
Roman numeral will appear here- Two-way conversion: Arabic to Roman and Roman to Arabic
- Real-time conversion as you type
- Validation with clear error messages
- Reference table and common examples
- One-click copy output
- 100% browser — no server calls
What is Roman Numeral Converter?
A Roman numeral converter is an online tool that translates between the modern Arabic number system (1, 2, 3...) and the ancient Roman numeral system (I, II, III...).
Roman numerals use seven symbols — I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) — combined according to specific rules to represent any number from 1 to 3999. The standard Roman numeral system uses subtractive notation where placing a smaller value before a larger one means subtraction (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900). This converter works in both directions: enter an Arabic number to get the Roman numeral equivalent, or enter a Roman numeral to get the Arabic number. The tool validates input in real time, catching invalid combinations and out-of-range values instantly. All conversion runs entirely in your browser with zero server interaction, making it fast and private.
How to use Roman Numeral Converter
- 1
Select your conversion mode
Choose between "Number to Roman" to convert Arabic numbers (like 2026) into Roman numerals, or "Roman to Number" to convert Roman numerals (like MMXXVI) back into Arabic numbers. Click the toggle buttons at the top to switch modes.
- 2
Enter your value
Type your number or Roman numeral into the input field. The converter works in real time — your result appears instantly as you type. For Arabic numbers, enter any whole number from 1 to 3999. For Roman numerals, use the letters M, D, C, L, X, V, and I.
- 3
Copy or explore examples
Click the Copy button next to the output to copy the result to your clipboard. Use the common examples section to quickly load popular conversions like years, clock numbers, or the maximum value 3999. The reference table shows all seven Roman numeral symbols and their values.
Everything this tool
does for you
- Two-way conversion between Arabic numbers and Roman numerals with a single toggle
- Real-time conversion that updates instantly as you type each character
- Input validation with clear error messages for invalid numbers or numeral combinations
- Reference table showing all seven Roman numeral symbols (I, V, X, L, C, D, M) and their values
- Eight common examples including years, clock numbers, and edge cases you can load with one click
- Round-trip validation ensures Roman numeral output matches standard canonical form
- One-click copy button to copy the converted result to your clipboard instantly
- Zero server calls — all conversion logic runs entirely in your browser for instant results
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