What range of numbers can I convert?

Standard Roman numerals cover 1 to 3999. Values outside this range, or non-whole numbers, are flagged as errors since classic Roman numerals have no symbol for zero or numbers above 3999.

Why does it reject some Roman numerals like IIII?

The converter validates against the canonical form. Repetitions and subtractive pairs must follow standard rules, so non-standard spellings such as IIII (instead of IV) are rejected as invalid.

🏛️

Roman Numeral Converter

Convert numbers to Roman numerals and back.

Loading tool…

How to use the Roman Numeral Converter

1Type a number from 1 to 3999 into the Number field.
2The Roman numeral updates instantly, or edit the Roman field to decode it.
3Copy either result with one click.

About the Roman Numeral Converter

Free online Roman numeral converter. Instantly translate numbers (1-3999) to Roman numerals and decode Roman numerals back to numbers with live validation.

Part of our Unit Converters collection. Browse all tools.

Frequently asked questions

What range of numbers can I convert?: Standard Roman numerals cover 1 to 3999. Values outside this range, or non-whole numbers, are flagged as errors since classic Roman numerals have no symbol for zero or numbers above 3999.
Why does it reject some Roman numerals like IIII?: The converter validates against the canonical form. Repetitions and subtractive pairs must follow standard rules, so non-standard spellings such as IIII (instead of IV) are rejected as invalid.