Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers, instantly and accurately (1-3999).
Result appears hereRoman numeral reference
About this tool
This Roman numeral converter works in both directions: type a regular number from 1 to 3999 to see its Roman numeral form, or type a Roman numeral to read its value as an ordinary number. It uses standard subtractive notation, the same system carved on monuments and clocks, where IV means 4 and IX means 9. The result updates as you type, can be copied with one click, and a reference chart shows the seven base symbols. Everything runs in your browser, so it is instant and works offline once loaded.
How to use
- 1 Choose a direction: Number to Roman, or Roman to Number.
- 2 Type your value in the input box; the conversion happens as you type.
- 3 Read the converted result below and use the copy button to grab it.
- 4 Check the reference chart for the seven base symbols (I, V, X, L, C, D, M).
How it works
Roman numerals combine seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. To build a numeral the tool repeatedly subtracts the largest value it can, using the subtractive pairs IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900) so that no symbol repeats more than three times. To read a numeral it scans left to right, adding each symbol's value but subtracting it when a smaller symbol sits before a larger one. The result is then checked against the canonical spelling, so non-standard forms such as IIII or VV are rejected. The classic system has no symbol for zero and no standard way to write numbers above 3999, which is why the range is 1 to 3999.
Frequently asked questions
What range of numbers can I convert?
You can convert any whole number from 1 to 3999. Classic Roman numerals have no symbol for zero or negative numbers, and writing values above 3999 requires bars or other notations that are not part of the standard system, so the converter limits the range to 1-3999.
How does subtractive notation work?
Instead of writing four identical symbols, Roman numerals place a smaller symbol before a larger one to subtract: IV is 4 (5 minus 1), IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. That is why 1994 is MCMXCIV rather than a long string of repeated letters.
Why is my Roman numeral shown as invalid?
The converter only accepts the standard spelling of each number. Forms like IIII, VV or IC break the rules (a symbol repeating more than three times, or an illegal subtraction), so they are flagged as invalid even though people sometimes write them informally, such as IIII on clock faces.
How do I write the year 2024 in Roman numerals?
2024 is MMXXIV: MM is 2000, XX is 20 and IV is 4. You can confirm any year by typing it into the Number to Roman tab, then switch tabs to convert it back and check the result matches.
Related tools and uses
Roman numerals appear on clock faces, book chapters, movie sequels, monument dates and the Super Bowl, so this converter is handy for students, designers and history buffs alike. Pair it with the number base converter for binary and hexadecimal, the scientific notation tool for very large numbers, and the percentage calculator for everyday math.