Roman numeral converter
Convert numbers and Roman numerals in either direction, with a breakdown of additive and subtractive symbols.
How it works & useful details
How it works & limits
Supports canonical Roman numerals from I (1) to MMMCMXCIX (3,999). Uppercase and lowercase input are accepted; output is uppercase. Subtractive pairs are IV, IX, XL, XC, CD, and CM.
Nonstandard spellings such as IIII, IC, or VX are rejected. Zero, negative numbers, fractions, and overbar notation are outside this tool's scope.
Your working space
Change the values to explore the preview. Use the action below to create a copyable, downloadable result. All calculations stay on this device; refreshing clears your work.
About this tool
Roman numeral converter translates between integers and Roman numerals in either direction, and breaks the result into the additive and subtractive symbols that produced it. It is handy for dates, chapter numbers, and historical documents.
The converter follows standard Roman numeral rules, including the subtractive forms such as IV and CM, and reports when an input cannot be represented. All processing is local.
How to use it
- Choose the direction: number to numeral, or numeral to number.
- Enter the value.
- Read the converted result and the symbol breakdown.
- Copy the result for your document.
Worked example
1994 becomes MCMXCIV, read from the largest value down:
- M = 1000
- CM = 900 (100 before 1000, subtractive)
- XC = 90 (10 before 100, subtractive)
- IV = 4 (1 before 5, subtractive)
The symbols are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. A smaller symbol placed before a larger one is subtracted, but only in six standard pairs: IV, IX, XL, XC, CD, and CM.
Why some spellings are rejected
Clock faces often show 4 as IIII, and you may see forms like IC for 99 or MIM for 1999. They look plausible, but they are not the canonical modern form, and accepting them would make round trips ambiguous. The converter only accepts the standard spelling, so a numeral it accepts always converts back to exactly the same numeral.
Roman numerals have no zero and no standard way to write fractions. Standard notation stops at 3,999 (MMMCMXCIX). Larger values historically used a bar over the symbols to multiply by 1,000, which is outside this tool's scope. Common uses today are years on buildings and film credits, monarch and event names, outline numbering, and book front matter.
Frequently asked questions
What is the valid range?
Standard Roman numerals represent one to a few thousand. Values outside that range are reported rather than invented.
Are non-standard forms rejected?
Yes. Inputs like IIII or VX are reported instead of being silently normalized, so the conversion stays unambiguous.
Is lowercase accepted?
Lowercase numerals are accepted as input and reported in the standard uppercase form.