Everyday tool
Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals to numbers, with strict validation of the rules, a breakdown of each symbol and a quick reference.
Free, no sign-up. Runs in your browser; nothing is uploaded.
Number to Roman numeral
M = 1000, M = 1000, X = 10, X = 10, IV = 4
Roman numeral to number
Reference
A smaller letter before a larger one is subtracted (IV is 4, CM is 900). Only I, X and C can be subtracted, and a letter repeats at most three times in a row.
How to use the roman numeral converter
Roman numerals, converted and checked
Roman numerals still appear on clocks, book chapters, film copyright dates, monarch names and tattoos. This converter works in both directions and tells you when a numeral breaks the rules.
Number to Roman numeral
Type any whole number from 1 to 3999. The result appears at once with a breakdown, such as M = 1000, M = 1000, X = 10, X = 10, V = 5, I = 1 for 2026 (MMXXVI). Copy it with one click.
Roman numeral to number
Enter letters from I, V, X, L, C, D and M in any case. With Strict on, the numeral must be in standard form. If it is not, the tool explains why and shows the standard form, so a mistyped IIX is flagged and the correct VIII is suggested. Turn Strict off to accept variants such as IIII for 4; the tool then adds a note showing the standard spelling.
The rules in short
- Symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.
- Add when symbols decrease or repeat: VIII is 8, XXX is 30.
- Subtract when a smaller symbol comes before a larger one: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400, CM is 900.
- Repeat I, X, C and M up to three times. V, L and D never repeat.
- Limit: standard numerals run from 1 to 3999.
Handy examples
- 1994 is MCMXCIV: M, then CM, then XC, then IV.
- 49 is XLIX, not IL. Subtraction is only allowed for the pairs listed above.
- 2000 is MM.
Tips for use
When writing a year on a document or monument, double-check by converting it back. For chapter or outline numbering, copy numerals directly from the result. The reference panel at the bottom lists each symbol for quick learning.
Frequently asked questions
What is the largest number I can convert?
3999 (MMMCMXCIX). The standard system has no symbol above M, and numbers beyond 3999 would need an overline notation that is not widely supported.
Why is there no zero?
The Roman system had no symbol for zero, so only whole numbers from 1 upwards can be written.
Why is IIII flagged as invalid?
Standard form uses subtraction, so 4 is IV. Clock faces often show IIII, which is a historical variant. Turn off Strict mode to accept it with a note.
What are the subtraction rules?
Only I, X and C can come before a larger letter: I before V or X, X before L or C, C before D or M. A letter repeats at most three times in a row.
How do I write a year?
Enter it as a number, for example 2026 becomes MMXXVI. Use the shortcut buttons to try common years.
Is anything sent anywhere?
No. The conversion happens in your browser.