Roman Numeral Converter
Convert between Roman numerals and decimal numbers (1–3999).
The Roman Numeral Converter translates between modern decimal (Arabic) numbers and traditional Roman numerals. It supports the standard range of 1 through 3999, which covers the full set of values expressible with the seven Roman numeral symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000).
Roman numerals remain widely used today. They appear on clock faces, in movie copyright dates, as chapter and section numbers in books, in outlines and legal documents, and as part of names for monarchs and popes. Super Bowl numbering and Olympic Games also use Roman numerals prominently.
In Decimal to Roman mode, enter a whole number between 1 and 3999 and the tool produces the correct Roman numeral representation using subtractive notation (for example, IV instead of IIII for 4, and IX instead of VIIII for 9). In Roman to Decimal mode, enter a Roman numeral string and the tool calculates the corresponding decimal integer.
The converter validates inputs in both directions. Decimal values outside the 1–3999 range are rejected, and invalid Roman numeral characters produce an error. All processing runs in your browser using JavaScript. No data is sent to any server and no sign-up is needed.
Roman numerals remain widely used today. They appear on clock faces, in movie copyright dates, as chapter and section numbers in books, in outlines and legal documents, and as part of names for monarchs and popes. Super Bowl numbering and Olympic Games also use Roman numerals prominently.
In Decimal to Roman mode, enter a whole number between 1 and 3999 and the tool produces the correct Roman numeral representation using subtractive notation (for example, IV instead of IIII for 4, and IX instead of VIIII for 9). In Roman to Decimal mode, enter a Roman numeral string and the tool calculates the corresponding decimal integer.
The converter validates inputs in both directions. Decimal values outside the 1–3999 range are rejected, and invalid Roman numeral characters produce an error. All processing runs in your browser using JavaScript. No data is sent to any server and no sign-up is needed.
Converter
Results
—
How to Use
- Select the conversion direction: Decimal to Roman or Roman to Decimal.
- Enter a number (1–3999) or a Roman numeral string.
- View the converted result.
FAQ
Why is the range limited to 1–3999?
Standard Roman numerals use seven symbols (I, V, X, L, C, D, M) and can only represent values up to 3999 (MMMCMXCIX) without using extended notation with overbars.
What is subtractive notation?
Subtractive notation places a smaller numeral before a larger one to indicate subtraction. For example, IV means 5 minus 1 equals 4, and XC means 100 minus 10 equals 90.
Does this accept lowercase Roman numerals?
Yes. The tool accepts both uppercase (XIV) and lowercase (xiv) Roman numeral input.
Is my data safe in the browser?
Yes. All calculations run locally in your browser using JavaScript. No data is sent to any server.
Part of These Collections
Curated tool sets for specific workflows
Thank you! Your report has been submitted.