Roman Numerals Converter by Joel Christophel is a free Android utility that allows you to convert Roman numerals to Arabic (decimal) numbers and vice versa. The app is lightweight with a download size of only 0.15 MB and requires no permissions.

The app is designed to handle two-way conversion of Roman numerals between 1 and 3,999,999. It supports five operations: exponentiation, multiplication, division, addition, and subtraction. Parentheses and decimal points are also supported. The app follows the correct order of operations and can interpret expressions consisting of Roman numerals, Arabic (decimal) numbers, and a combination of the two. It can also reformat improper Roman numerals and simplify expressions.

Roman Numerals Converter has a user-friendly interface that displays the output as you type. The app also offers copy/paste functionality and a custom keyboard. It is available in English, Spanish, and Russian. Overall, Roman Numerals Converter is an efficient and reliable tool for anyone who needs to convert Roman numerals to Arabic numbers or vice versa.