Roman Numeral Converter
This Roman numeral converter changes Roman numerals into regular Arabic numbers and turns ordinary numbers back into Roman numerals. It is built for anyone reading a clock face, decoding a movie sequel, writing a date or birth year for a tattoo, or just checking how a number is spelled in Roman.
You do not pick a direction first. Type a value and the tool detects whether you entered an Arabic number or a Roman numeral, then converts it instantly. Convert one value in Single mode, paste a long list in Batch mode, or generate a full sequence such as 1 to 100 in Range mode. A compact symbol reference (I = 1 through M = 1000) stays visible the whole time.
How to Use the Roman Numeral Converter
Pick the mode that matches your task. Single converts one value at a time, Batch handles a whole list, and Range builds a sequence of numerals.
Single: type and read
In Single mode, type a number from 1 to 3999 or a Roman numeral into the input. A badge shows the detected direction (Arabic → Roman or Roman → Arabic), the result appears as you type, and you can Copy it with one click.
Batch: convert a list
Open the Batch tab and enter one number or numeral per line. Each result lines up beside its input, the header shows how many converted, and Copy All copies every result at once. Use Clear to start over.
Range: generate a sequence
Open the Range tab, set a Start and End, then click Generate or press Enter. Choose Roman only or Both (Arabic and Roman side by side), or tap a preset such as 1-10, 1-50, 1-100, 1-500, or 1-1000.
Try the examples
Click any example button to load a common conversion. Examples are grouped into Arabic values (1, 4, 9, 49, 99, 2024 and more) and Roman numerals (IV, XIV, MCMXCIX and more) so you can test quickly.
Features
Bidirectional Conversion
Convert Arabic numbers to Roman numerals and Roman numerals back to Arabic numbers in the same tool.
Auto-Detection
No need to choose a direction. The converter reads your input and decides whether it is a number or a Roman numeral.
Real-Time Results
Single and Batch modes update the result as you type, with no convert button to press.
Three Conversion Modes
Single for one value, Batch for many values one per line, and Range to generate a full sequence.
Format Options
In Range mode, show Roman numerals only or both the Arabic and Roman values side by side.
Quick Presets
One tap fills common ranges in Range mode: 1-10, 1-50, 1-100, 1-500, and 1-1000.
Input Validation
Clear messages flag numbers outside 1 to 3999, invalid Roman patterns, and unrecognized characters.
One-Click Copy
Copy a single result, or use Copy All to copy every result from Batch and Range modes at once.
Quick Reference
A compact chart of every symbol and value (I = 1 to M = 1000) stays on screen for easy lookup.
How Roman Numerals Work
Roman numerals combine seven letters from the Latin alphabet, each standing for a fixed value:
Letters add up when they go from larger to smaller, but Roman numerals also use subtractive notation to avoid four identical symbols in a row: a smaller letter placed before a larger one is subtracted. That is why 4 is IV (5 - 1) rather than IIII, and 9 is IX (10 - 1). The same pattern gives XL = 40, XC = 90, CD = 400, and CM = 900.
Frequently Asked Questions
How do I convert a number to Roman numerals?
Type the number (1 to 3999) into the Single input. The tool detects it as an Arabic number, shows the Arabic → Roman badge, and displays the Roman numeral as you type. Click Copy to grab the result.
How do I read a Roman numeral as a number?
Type the Roman numeral into the Single input. It is detected as Roman, the Roman → Arabic badge appears, and the equivalent number is shown instantly.
How do I write a date or birth year in Roman numerals?
Years up to 3999 convert directly: type 2024 to get MMXXIV, or 1999 to get MCMXCIX. For a full date, convert the day, month, and year separately and combine them. Try the 2024 example button for a quick start.
What are the rules behind Roman numerals?
Symbols are normally added from largest to smallest, and I, X, C, and M repeat at most three times. To avoid four in a row, a smaller symbol before a larger one is subtracted (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900). The symbols V, L, and D never repeat. The converter enforces these rules and flags inputs that break them.
Why is 4 written IV and not IIII?
Standard Roman numerals avoid four identical symbols in a row, so 4 uses subtractive notation: I before V means 5 - 1 = 4. Entering IIII is treated as an invalid Roman numeral by this converter.
What is the largest number this tool can convert?
The standard system covers 1 to 3999. The largest value is 3999, written MMMCMXCIX. Numbers above 3999 need special bar (vinculum) notation, which this tool does not cover. There is also no symbol for 0 or for negative numbers.
How do I generate Roman numerals from 1 to 100?
Open Range mode, set Start to 1 and End to 100, then click Generate, or just tap the 1-100 preset. A range can span up to 1000 numbers, and Copy All copies the whole list.
Is my data stored or sent anywhere?
No. Every conversion happens directly in your browser. Your input is never sent to a server or saved anywhere.
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