Math

Roman Numeral Converter

Convert numbers from 1 to 3999 into Roman numerals, or read a Roman numeral back into a number.

Number (1 to 3999)

Roman numeral

How to use it

Type a number from 1 to 3999 to get its Roman numeral.
Or type a Roman numeral to get the number.
Use the info line if the input is not valid.

How it works and why it matters

Roman numerals use letters such as I, V, X, L, C, D and M. Standard Roman numerals stop at 3999 (MMMCMXCIX), because there is no common symbol for larger numbers. The converter also checks that a Roman numeral follows the standard rules, so invalid forms like IIII are reported.

Questions

What is the largest Roman numeral?

The standard limit is 3999 (MMMCMXCIX). Larger numbers need special notation not covered here.

Why is IIII not valid?

Standard Roman numerals use IV for four. The validation follows this standard, though some clocks and inscriptions use IIII.

Can I use lowercase letters?

Yes. The converter accepts lowercase and turns it into uppercase.