Roman numeral arithmetic
Roman Numeral Calculator
Add, subtract, multiply, or divide two validated Roman numerals with Arabic values, representability checks, and calculation steps.
Enter canonical uppercase or lowercase Roman numerals from I through MMMCMXCIX. Zero, negative values, and non-integer division results have no supported Roman output.
Loading local Roman arithmetic…
Calculation result
Operand 1:
Operand 2:
Arabic result:
Roman result:
Method, ownership, and limits
Inputs are parsed with strict canonical Roman syntax and converted by positional subtraction. Results reuse the exact toRoman implementation from C467’s shared Roman/date core. Addition, subtraction, multiplication, and division operate on the Arabic values. Roman output is shown only for whole results from 1 through 3999.
This page owns arithmetic. Use Roman Numeral Converter for conversion only and Roman Numeral Date Converter for calendar-date formatting.
Inputs and results stay in this browser tab. They are not placed in URLs, saved in browser storage, or sent to a remote calculation service.