Utilities
Roman Numeral Converter
Convert numbers between decimal (1-3999) and Roman numerals locally in your browser.
Convert a decimal number from 1 to 3999 into Roman numerals, or convert a Roman numeral from I to MMMCMXCIX back into decimal. Conversions run privately in your browser; your value is not uploaded or stored.
Convert one number into the form you need.
Enter a decimal number from 1 to 3999 to see its Roman numeral, or enter a Roman numeral from I to MMMCMXCIX to see its decimal value. Standard subtractive notation is used, and everything runs locally in your browser, so your value is not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
Which values can I convert?
Enter a whole decimal number from 1 to 3999, or enter a Roman numeral from I to MMMCMXCIX. The converter returns both the Roman numeral and the decimal value using standard subtractive notation.
How does subtractive notation work?
Roman numerals normally use subtractive pairs such as IV for 4, IX for 9, XL for 40, XC for 90, CD for 400, and CM for 900. For example, 14 is written as XIV and 1994 is written as MCMXCIV.
Why is an input rejected?
Decimal input must be a whole number from 1 to 3999 because standard Roman numerals have no zero, negatives, fractions, or values above MMMCMXCIX. Roman-numeral input must use only the letters M, D, C, L, X, V, and I in valid standard form, so spellings such as IIII or VV show a clear error instead of a result.
Does my value leave my browser?
No. The conversion and copy action run locally in your browser. CodeASystem does not upload or store the value you enter.